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<h1>Developing Geospatial software with Python, Part 1</h1>
<h2>GFOSS Day, Foligno - 18/19 November 2010</h2>
</div>
</div>
<div class="presentation">
<div class="slide" id="slide0">
<h1 class="title">Developing Geospatial software with Python, Part 1</h1>
<h2 class="subtitle" id="alessandro-pasotti-apasotti-gmail-com-paolo-corti-pcorti-gmail-com">Alessandro Pasotti (<a class="reference external" href="mailto:apasotti@gmail.com">apasotti@gmail.com</a>), Paolo Corti (<a class="reference external" href="mailto:pcorti@gmail.com">pcorti@gmail.com</a>)</h2>
<p>License:
Creative Commons Attribution - Share Alike 3.0</p>
</div>
<div class="slide" id="summary">
<h1>Summary</h1>
<p><strong>Part 1 - Paolo Corti</strong></p>
<ul class="simple">
<li><strong>GDAL/OGR (Python bindings, GeoDjango)</strong></li>
<li><strong>GEOS (GeoDjango, Shapely)</strong></li>
<li><strong>PROJ.4 (Python bindings, GeoDjango)</strong></li>
<li><strong>GeoAlchemy</strong></li>
</ul>
<p>Part 2 - Alessandro Pasotti</p>
<ul class="simple">
<li>OWS (OWSLib, pyWPS)</li>
<li>WebServices (GeoPy, Mapnik, Mapscript)</li>
<li>Desktop (QGIS, GRASS)</li>
</ul>
</div>
<div class="slide" id="building-blocks">
<h1>Building blocks</h1>
<ul>
<li><dl class="first docutils">
<dt><strong>GDAL</strong> Geospatial Data Abstraction Library</dt>
<dd><ul class="first last simple">
<li><strong>OGR</strong> Simple Feature Library</li>
</ul>
</dd>
</dl>
</li>
<li><p class="first"><strong>GEOS</strong> Geometry Engine, Open Source</p>
</li>
<li><p class="first"><strong>PROJ.4</strong> Cartographic Projections Library</p>
</li>
</ul>
</div>
<div class="slide" id="building-blocks-gdal-ogr">
<h1>Building blocks: GDAL/OGR</h1>
<dl class="docutils">
<dt><strong>GDAL</strong> Geospatial Data Abstraction Library</dt>
<dd><strong>OGR</strong> Simple Feature Library</dd>
</dl>
<ul class="simple">
<li>basic library for almost all FOSS4G projects (and often proprietary projects)</li>
<li>library and utilities for reading/writing a plethora of GIS formats</li>
<li>raster/cover (GDAL) and vectorial (OGR)</li>
<li>OGR follows the OGC Simple feature access specifications</li>
<li>written mostly in C++ by Frank Warmerdam</li>
<li>license: <strong>X/MIT</strong></li>
</ul>
</div>
<div class="slide" id="gdal-ogr-large-diffusion">
<h1>GDAL/OGR: large diffusion</h1>
<blockquote>
Large list of sofware using GDAL, here only most important (full list @ GDAL website)</blockquote>
<ul class="simple">
<li><strong>FOSS4G</strong>: GRASS, GeoServer, gvSIG, MapServer, MapGuide, Orfeo Toolbox, OSSIM, QGIS, R</li>
<li><strong>proprietary</strong>: ArcGis, ERDAS, FME, Google Earth</li>
</ul>
</div>
<div class="slide" id="gdal-ogr-vector-formats">
<h1>GDAL/OGR: vector formats</h1>
<blockquote>
<p>Long list too, here only most important (full list @ gdal website)</p>
<p>OGR (Vector) (get the full list with <strong>ogrinfo --formats</strong>):</p>
</blockquote>
<ul class="simple">
<li><strong>FOSS4G</strong> (RW): PostGis, Spatialite, MySQL, csv, GeoJSON, GeoRSS, GML, GPSBabel, GPX, GRASS, KML, WFS</li>
<li><strong>proprietary</strong>: Shapefile, ArcInfo Coverage (R), ArcInfo .E00 (R), AutoCAD DXF, Esri PGDB (R), ArcSde (R), FMEObjects Gateway (R), MapInfo, Microstation DGN, Oracle Spatial, Microsoft MS Spatial</li>
</ul>
</div>
<div class="slide" id="gdal-ogr-raster-formats">
<h1>GDAL/OGR: raster formats</h1>
<blockquote>
GDAL (Raster) (get the full list with <strong>gdalinfo --formats</strong>):</blockquote>
<ul class="simple">
<li><strong>FOSS4G</strong> (RW): GRASS Rasters, WKTRaster, Rasterlite</li>
<li><strong>proprietary</strong>: ArcInfo ASCII Grid, ArcSde Raster (R), ERDAS (R), Oracle Spatial GeoRaster, Intergraph, TIFF/GeoTIFF (Adobe)</li>
</ul>
</div>
<div class="slide" id="gdal-ogr-bindings">
<h1>GDAL/OGR: bindings</h1>
<blockquote>
bindings (based on SWIG) provide the GDAL power to developers using other languages than C/C++</blockquote>
<ul class="simple">
<li><strong>Python</strong></li>
<li>Perl</li>
<li>VB6 (COM) - No SWIG</li>
<li>Ruby</li>
<li>Java</li>
<li>.Net (VB, C#, ...)</li>
<li>R</li>
</ul>
</div>
<div class="slide" id="gdal-ogr-utilities-raster">
<h1>GDAL/OGR: utilities (raster)</h1>
<blockquote>
The power of GDAL/OGR at your fingertips (mostly in c, cpp but some written in python)!</blockquote>
<ul class="simple">
<li>gdalinfo: info about a file</li>
<li>gdal_translate: copy a raster with control on output</li>
<li>gdal_rasterize: rasterize vectors</li>
<li>gdalwarp: warp an image into a new coordiante system</li>
<li>gdaltransform: transform coordinates</li>
<li>gdal_retile.py: build tiled pyramid levels</li>
<li>gdal_grid: create raster from scattered data</li>
<li>gdal_polygonize.py: generate polygons from raster</li>
</ul>
</div>
<div class="slide" id="gdal-ogr-utilities-vector">
<h1>GDAL/OGR: utilities (vector)</h1>
<ul class="simple">
<li>ogrinfo: lists information about an OGR supported data source</li>
<li>ogr2ogr: converts simple features data between file formats</li>
<li>ogrtindex: creates a tileindex</li>
</ul>
</div>
<div class="slide" id="building-blocks-geos">
<h1>Building blocks: GEOS</h1>
<ul class="simple">
<li>it is a C++ port of <strong>JTS</strong> (Java Topology Suite from Vivid Solutions)</li>
<li>originally started from Refractions for PostGIS</li>
<li>provides all the <strong>OGC Simple Feature Access</strong> implementations for SQL spatial predicate functions and spatial operators</li>
<li>license: <strong>LGPL</strong></li>
</ul>
</div>
<div class="slide" id="geos-geometry-engine-open-source">
<h1>GEOS: Geometry Engine, Open Source</h1>
<p><strong>GEOS</strong> Geometry Engine, Open Source</p>
<ul class="simple">
<li><strong>model for geometric objects</strong> (Point, Linestring, Polygon, Multipoint, Multipolygon, GeomCollection)</li>
<li><strong>geometric attributes and methods</strong> (empty, geom_type, num_coords, centroid, area, distance, length, srs, transform...)</li>
<li><strong>representation and interoperation</strong> (ewkt, hex, hexewkb, json, geojson, kml, ogr, wkb, ewkb, wkt)</li>
<li><strong>unary predicates</strong> (has_z, simple, valid...)</li>
<li><strong>binary predicates</strong> (contains, crosses, equals, intersects, touches, within, ...)</li>
<li><strong>constructive spatial analysis methods</strong> (buffer, difference, intersection, simplify, union, envelope, ...)</li>
</ul>
</div>
<div class="slide" id="geos-huge-diffusion">
<h1>GEOS: huge diffusion</h1>
<blockquote>
Large list of sofware using GEOS, here only most important (full list @ GEOS website)</blockquote>
<ul class="simple">
<li><strong>FOSS4G</strong>: PostGIS, Spatialite, MapServer, QGIS, OGR, Shapely, GeoDjango</li>
<li><strong>proprietary</strong>: FME, Autodesk MapGuide Enterprise</li>
</ul>
</div>
<div class="slide" id="geos-bindings">
<h1>GEOS: bindings</h1>
<blockquote>
bindings provide the GEOS power to developers using other languages than C/C++</blockquote>
<ul class="simple">
<li><strong>Python</strong> (not maintained anymore --> <strong>GeoDjango, Shapely</strong>)</li>
<li>Ruby</li>
<li>PHP</li>
</ul>
<p>Java developers of course must use the JTS!</p>
<p>.NET developers can use the .NET JTS port (NetTopologySuite)</p>
</div>
<div class="slide" id="building-blocks-proj-4">
<h1>Building blocks: PROJ.4</h1>
<p><strong>PROJ.4</strong> Cartographic Projections Library</p>
<ul class="simple">
<li>PROJ.4 Cartographic Projections library originally written by Gerald Evenden then of the USGS</li>
<li>written in C/C++</li>
<li>both a <strong>command line</strong> and an <strong>API</strong></li>
<li>used from almost any FOSS4G project</li>
<li>ported to javascript (<strong>Proj4js</strong>) and Java (<strong>Proj4J</strong>)</li>
<li>license: <strong>MIT</strong></li>
</ul>
</div>
<div class="slide" id="proj-4-api">
<h1>PROJ.4: API</h1>
<p>Just 2 methods available:</p>
<ul class="simple">
<li>create a projPJ coordinate system object from the string definition</li>
<li>transform the x/y/z points from the source coordinate system to the destination coordinate system:</li>
</ul>
<div class="highlight"><pre>projPJ pj_init_plus<span class="o">(</span>const char *definition<span class="o">)</span>;
int pj_transform<span class="o">(</span> projPJ srcdefn, projPJ dstdefn, long point_count, int point_offset, double *x, double *y, double *z <span class="o">)</span>;
</pre></div>
</div>
<div class="slide" id="implementations">
<h1>Implementations</h1>
<ul class="simple">
<li><strong>GDAL/OGR bindings</strong>: Python API to GDAL/OGR, PROJ.4 and GEOS (parts of)</li>
<li><strong>GeoDjango</strong>: Python API to GDAL/OGR, PROJ.4 and GEOS plus other goodness</li>
<li><strong>Shapely</strong>: Python API to GEOS</li>
<li><strong>GeoAlchemy</strong>: Python API integrating SQLAlchemy for spatial database support</li>
</ul>
</div>
<div class="slide" id="id1">
<h1>GDAL/OGR bindings</h1>
<ul class="simple">
<li>GDAL/OGR library offers Python bindings generated by <strong>SWIG</strong></li>
<li>GDAL is for raster, OGR for vector</li>
<li>GDAL Python bindings is the <strong>only solution for raster</strong></li>
<li>documentation to be improved</li>
<li>license: <strong>X/MIT</strong></li>
</ul>
</div>
<div class="slide" id="gdal-ogr-bindings-gdal-example-1">
<h1>GDAL/OGR bindings: GDAL example (1)</h1>
<blockquote>
accessing the raster, getting the projection and reading general properties</blockquote>
<div class="highlight"><pre><span class="o">>>></span> <span class="kn">from</span> <span class="nn">osgeo</span> <span class="kn">import</span> <span class="n">gdal</span>
<span class="o">>>></span> <span class="n">ds</span> <span class="o">=</span> <span class="n">gdal</span><span class="o">.</span><span class="n">Open</span><span class="p">(</span><span class="s">'aster.img'</span><span class="p">,</span> <span class="n">gdal</span><span class="o">.</span><span class="n">GA_ReadOnly</span><span class="p">)</span>
<span class="o">>>></span> <span class="n">ds</span><span class="o">.</span><span class="n">GetProjection</span><span class="p">()</span>
<span class="s">'PROJCS["UTM Zone 12, Northern Hemisphere",...AUTHORITY["EPSG","32612"]]'</span>
<span class="o">>>></span> <span class="k">print</span> <span class="s">'Raster has </span><span class="si">%s</span><span class="s"> cols, </span><span class="si">%s</span><span class="s"> rows'</span> <span class="o">%</span> <span class="p">(</span><span class="n">ds</span><span class="o">.</span><span class="n">RasterXSize</span><span class="p">,</span> <span class="n">ds</span><span class="o">.</span><span class="n">RasterYSize</span><span class="p">)</span>
<span class="n">Raster</span> <span class="n">has</span> <span class="mi">5665</span> <span class="n">cols</span><span class="p">,</span> <span class="mi">5033</span> <span class="n">rows</span>
<span class="o">>>></span> <span class="k">print</span> <span class="s">'Raster has </span><span class="si">%s</span><span class="s"> bands'</span> <span class="o">%</span> <span class="n">ds</span><span class="o">.</span><span class="n">RasterCount</span>
<span class="n">Raster</span> <span class="n">has</span> <span class="mi">3</span> <span class="n">bands</span>
</pre></div>
</div>
<div class="slide" id="gdal-ogr-bindings-gdal-example-2">
<h1>GDAL/OGR bindings: GDAL example (2)</h1>
<blockquote>
accessing the raster geotrasform parameters - aka the georeferencing information</blockquote>
<div class="highlight"><pre><span class="o">>>></span> <span class="n">geotransform</span> <span class="o">=</span> <span class="n">ds</span><span class="o">.</span><span class="n">GetGeoTransform</span><span class="p">()</span>
<span class="o">>>></span> <span class="k">print</span> <span class="n">geotransform</span>
<span class="p">(</span><span class="mf">419976.5</span><span class="p">,</span> <span class="mf">15.0</span><span class="p">,</span> <span class="mf">0.0</span><span class="p">,</span> <span class="mf">4662422.5</span><span class="p">,</span> <span class="mf">0.0</span><span class="p">,</span> <span class="o">-</span><span class="mf">15.0</span><span class="p">)</span>
<span class="o">>>></span> <span class="k">print</span> <span class="s">'top left x is </span><span class="si">%s</span><span class="s">'</span> <span class="o">%</span> <span class="n">geotransform</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span>
<span class="n">top</span> <span class="n">left</span> <span class="n">x</span> <span class="ow">is</span> <span class="mf">419976.5</span>
<span class="o">>>></span> <span class="k">print</span> <span class="s">'top left y is </span><span class="si">%s</span><span class="s">'</span> <span class="o">%</span> <span class="n">geotransform</span><span class="p">[</span><span class="mi">3</span><span class="p">]</span>
<span class="n">top</span> <span class="n">left</span> <span class="n">y</span> <span class="ow">is</span> <span class="mf">4662422.5</span>
<span class="o">>>></span> <span class="k">print</span> <span class="s">'pixel width is </span><span class="si">%s</span><span class="s">'</span> <span class="o">%</span> <span class="n">geotransform</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span>
<span class="n">pixel</span> <span class="n">width</span> <span class="ow">is</span> <span class="mf">15.0</span>
<span class="o">>>></span> <span class="k">print</span> <span class="s">'pixel height is </span><span class="si">%s</span><span class="s">'</span> <span class="o">%</span> <span class="n">geotransform</span><span class="p">[</span><span class="mi">5</span><span class="p">]</span>
<span class="n">pixel</span> <span class="n">height</span> <span class="ow">is</span> <span class="o">-</span><span class="mf">15.0</span>
<span class="o">>>></span> <span class="k">print</span> <span class="s">'raster rotation is </span><span class="si">%s</span><span class="s">'</span> <span class="o">%</span> <span class="n">geotransform</span><span class="p">[</span><span class="mi">2</span><span class="p">]</span>
<span class="n">raster</span> <span class="n">rotation</span> <span class="ow">is</span> <span class="mf">0.0</span>
</pre></div>
</div>
<div class="slide" id="gdal-ogr-bindings-gdal-example-3">
<h1>GDAL/OGR bindings: GDAL example (3)</h1>
<blockquote>
reading the value of a cell for a given band (optimization issues, this is just a sample)</blockquote>
<div class="highlight"><pre><span class="o">>>></span> <span class="n">cols</span> <span class="o">=</span> <span class="n">ds</span><span class="o">.</span><span class="n">RasterXSize</span>
<span class="o">>>></span> <span class="n">rows</span> <span class="o">=</span> <span class="n">ds</span><span class="o">.</span><span class="n">RasterYSize</span>
<span class="o">>>></span> <span class="n">band1</span> <span class="o">=</span> <span class="n">ds</span><span class="o">.</span><span class="n">GetRasterBand</span><span class="p">(</span><span class="mi">1</span><span class="p">)</span>
<span class="o">>>></span> <span class="n">data</span> <span class="o">=</span> <span class="n">band1</span><span class="o">.</span><span class="n">ReadAsArray</span><span class="p">(</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span> <span class="n">cols</span><span class="p">,</span> <span class="n">rows</span><span class="p">)</span> <span class="o">//</span> <span class="mi">0</span><span class="p">,</span><span class="mi">0</span> <span class="ow">is</span> <span class="n">the</span> <span class="n">offset</span>
<span class="o">>>></span> <span class="n">value</span> <span class="o">=</span> <span class="n">data</span><span class="p">[</span><span class="mi">2000</span><span class="p">,</span><span class="mi">2000</span><span class="p">]</span>
<span class="o">>>></span> <span class="n">value</span>
<span class="mi">61</span>
</pre></div>
</div>
<div class="slide" id="gdal-ogr-bindings-ogr-example-1">
<h1>GDAL/OGR bindings: OGR example (1)</h1>
<blockquote>
reading a shapefile</blockquote>
<div class="highlight"><pre><span class="o">>>></span> <span class="kn">from</span> <span class="nn">osgeo</span> <span class="kn">import</span> <span class="n">ogr</span>
<span class="o">>>></span> <span class="n">driver</span> <span class="o">=</span> <span class="n">ogr</span><span class="o">.</span><span class="n">GetDriverByName</span><span class="p">(</span><span class="s">'ESRI Shapefile'</span><span class="p">)</span>
<span class="o">>>></span> <span class="n">datasource</span> <span class="o">=</span> <span class="n">driver</span><span class="o">.</span><span class="n">Open</span><span class="p">(</span><span class="s">'regioni.shp'</span><span class="p">,</span> <span class="mi">0</span><span class="p">)</span>
<span class="o">>>></span> <span class="k">print</span> <span class="n">datasource</span><span class="o">.</span><span class="n">GetLayerCount</span><span class="p">()</span>
<span class="mi">1</span>
<span class="o">>>></span> <span class="n">layer</span> <span class="o">=</span> <span class="n">datasource</span><span class="o">.</span><span class="n">GetLayer</span><span class="p">()</span>
<span class="o">>>></span> <span class="k">print</span> <span class="n">layer</span><span class="o">.</span><span class="n">GetFeatureCount</span><span class="p">()</span>
<span class="mi">20</span>
</pre></div>
</div>
<div class="slide" id="gdal-ogr-bindings-ogr-example-2">
<h1>GDAL/OGR bindings: OGR example (2)</h1>
<blockquote>
accessing shapefile metadata</blockquote>
<div class="highlight"><pre><span class="o">>>></span> <span class="n">srs</span> <span class="o">=</span> <span class="n">layer</span><span class="o">.</span><span class="n">GetSpatialRef</span><span class="p">()</span>
<span class="o">>>></span> <span class="k">print</span> <span class="n">srs</span><span class="o">.</span><span class="n">ExportToWkt</span><span class="p">()</span>
<span class="n">PROJCS</span><span class="p">[</span><span class="s">"UTM_Zone_32_Northern_Hemisphere"</span><span class="p">,</span><span class="n">GEOGCS</span><span class="p">[</span><span class="s">"GCS_International 1909 (Hayford)"</span><span class="p">,</span><span class="o">....</span>
<span class="o">>>></span> <span class="k">print</span> <span class="n">layer</span><span class="o">.</span><span class="n">GetExtent</span><span class="p">()</span>
<span class="p">(</span><span class="mf">313352.32445650722</span><span class="p">,</span> <span class="mf">1312130.1391031265</span><span class="p">,</span> <span class="mf">3933804.0026830882</span><span class="p">,</span> <span class="mf">5220607.6164360112</span><span class="p">)</span>
<span class="o">>>></span> <span class="n">layerDefn</span> <span class="o">=</span> <span class="n">layer</span><span class="o">.</span><span class="n">GetLayerDefn</span><span class="p">()</span>
<span class="o">>>></span> <span class="n">layerDefn</span><span class="o">.</span><span class="n">GetFieldCount</span><span class="p">()</span>
<span class="mi">9</span>
<span class="o">>>></span> <span class="n">layerDefn</span><span class="o">.</span><span class="n">GetGeomType</span><span class="p">()</span>
<span class="mi">3</span>
<span class="o">>>></span> <span class="n">fieldDefn</span> <span class="o">=</span> <span class="n">layerDefn</span><span class="o">.</span><span class="n">GetFieldDefn</span><span class="p">(</span><span class="mi">2</span><span class="p">)</span>
<span class="o">>>></span> <span class="n">fieldDefn</span><span class="o">.</span><span class="n">GetName</span><span class="p">()</span>
<span class="s">'REGIONE'</span>
<span class="o">>>></span> <span class="n">fieldDefn</span><span class="o">.</span><span class="n">GetTypeName</span><span class="p">()</span>
<span class="s">'String'</span>
</pre></div>
</div>
<div class="slide" id="gdal-ogr-bindings-ogr-example-3">
<h1>GDAL/OGR bindings: OGR example (3)</h1>
<blockquote>
accessing shapefile features and geometries</blockquote>
<div class="highlight"><pre><span class="o">>>></span> <span class="n">feature</span> <span class="o">=</span> <span class="n">layer</span><span class="o">.</span><span class="n">GetFeature</span><span class="p">(</span><span class="mi">0</span><span class="p">)</span>
<span class="o">>>></span> <span class="n">feature</span><span class="o">.</span><span class="n">GetFID</span><span class="p">()</span>
<span class="mi">0</span>
<span class="o">>>></span> <span class="n">feature</span><span class="o">.</span><span class="n">GetField</span><span class="p">(</span><span class="s">'REGIONE'</span><span class="p">)</span>
<span class="s">'PIEMONTE'</span>
<span class="o">>>></span> <span class="n">geometry</span> <span class="o">=</span> <span class="n">feature</span><span class="o">.</span><span class="n">GetGeometryRef</span><span class="p">()</span>
<span class="o">>>></span> <span class="n">geometry</span><span class="o">.</span><span class="n">GetEnvelope</span><span class="p">()</span>
<span class="p">(</span><span class="mf">313352.32445650722</span><span class="p">,</span> <span class="mf">517043.7912779671</span><span class="p">,</span> <span class="mf">4879624.4439933635</span><span class="p">,</span> <span class="mf">5146102.0567664672</span><span class="p">)</span>
<span class="o">>>></span> <span class="n">geometry</span><span class="o">.</span><span class="n">GetGeometryName</span><span class="p">()</span>
<span class="s">'MULTIPOLYGON'</span>
<span class="o">>>></span> <span class="n">geometry</span><span class="o">.</span><span class="n">IsValid</span><span class="p">()</span>
<span class="bp">True</span>
<span class="o">>>></span> <span class="n">geometry</span><span class="o">.</span><span class="n">GetDimension</span><span class="p">()</span>
<span class="mi">2</span>
</pre></div>
</div>
<div class="slide" id="gdal-ogr-bindings-ogr-example-4">
<h1>GDAL/OGR bindings: OGR example (4)</h1>
<blockquote>
accessing shapefile features and geometries</blockquote>
<div class="highlight"><pre><span class="o">>>></span> <span class="n">geometry</span><span class="o">.</span><span class="n">ExportToWkt</span><span class="p">()</span> <span class="c"># GML, KML, Wkb, Json</span>
<span class="s">'MULTIPOLYGON (((456956.454114792693872 5146065.056706172414124,...</span>
<span class="o">>>></span> <span class="n">geometry</span><span class="o">.</span><span class="n">GetArea</span><span class="p">()</span>
<span class="mf">25390743681.717426</span>
<span class="o">>>></span> <span class="n">poly0</span> <span class="o">=</span> <span class="n">geometry</span><span class="o">.</span><span class="n">GetGeometryRef</span><span class="p">(</span><span class="mi">0</span><span class="p">)</span>
<span class="o">>>></span> <span class="n">poly0</span><span class="o">.</span><span class="n">GetArea</span><span class="p">()</span>
<span class="mf">25390649513.408951</span>
<span class="o">>>></span> <span class="n">poly0</span><span class="o">.</span><span class="n">GetGeometryName</span><span class="p">()</span>
<span class="s">'POLYGON'</span>
<span class="o">>>></span> <span class="n">mybuffer</span> <span class="o">=</span> <span class="n">poly0</span><span class="o">.</span><span class="n">Buffer</span><span class="p">(</span><span class="mi">10000</span><span class="p">)</span>
<span class="o">>>></span> <span class="n">mybuffer</span><span class="o">.</span><span class="n">GetArea</span><span class="p">()</span>
<span class="mf">35462220275.922073</span>
</pre></div>
</div>
<div class="slide" id="gdal-ogr-bindings-resources">
<h1>GDAL/OGR bindings: resources</h1>
<ul class="simple">
<li>samples on svn: <a class="reference external" href="http://svn.osgeo.org/gdal/trunk/gdal/swig/python/samples/">http://svn.osgeo.org/gdal/trunk/gdal/swig/python/samples/</a></li>
<li>some GDAL command line utilities</li>
<li>many GDAL regression tests are written in Python: <a class="reference external" href="http://svn.osgeo.org/gdal/trunk/autotest/">http://svn.osgeo.org/gdal/trunk/autotest/</a></li>
<li>Geoprocessing with Python using OpenSource GIS: <a class="reference external" href="http://www.gis.usu.edu/~chrisg/python/2009/">http://www.gis.usu.edu/~chrisg/python/2009/</a></li>
<li>GDAL mailing list: <a class="reference external" href="http://lists.osgeo.org/mailman/listinfo/gdal-dev/">http://lists.osgeo.org/mailman/listinfo/gdal-dev/</a></li>
</ul>
</div>
<div class="slide" id="geodjango">
<h1>GeoDjango</h1>
<ul class="simple">
<li><strong>Django</strong>: The Web framework for perfectionists with deadlines. A <strong>DRY</strong> framework with an <strong>ORM</strong> (object relational mapper), a router, a <strong>MVC</strong> implementation and a great backend application</li>
<li><strong>GeoDjango</strong>: The Geographic Web Framework for perfectionists with deadlines</li>
<li>since Django 1.0 is a <strong>core package</strong></li>
<li>it is a framework including a set of API, utility and tool for developing GIS application with Django</li>
<li>as Django, you may use GeoDajngo both in <strong>web</strong> and <strong>desktop</strong> context</li>
<li>excellent documentation</li>
<li>license: <strong>BSD</strong></li>
</ul>
</div>
<div class="slide" id="geodjango-index">
<h1>GeoDjango: Index</h1>
<ul>
<li><p class="first"><strong>GeoDjango Architecture</strong></p>
</li>
<li><dl class="first docutils">
<dt><strong>GeoDjango main features</strong></dt>
<dd><ul class="first last simple">
<li>GeoDjango Model API</li>
<li>GEOS API</li>
<li>GDAL/OGR API</li>
<li>Measurement Units API</li>
<li>GeoDjango Admin site</li>
<li>Utilities (LayerMapping, OgrInspect)</li>
</ul>
</dd>
</dl>
</li>
</ul>
</div>
<div class="slide" id="geodjango-architecture">
<h1>GeoDjango: Architecture</h1>
<ul>
<li><dl class="first docutils">
<dt><strong>Spatial Database</strong></dt>
<dd><ul class="first last simple">
<li>PostGis</li>
<li>Spatialite</li>
<li>MySql (not OGC-compliant, limited functionality)</li>
<li>Oracle</li>
</ul>
</dd>
</dl>
</li>
<li><dl class="first docutils">
<dt><strong>GIS Libraries</strong> (Python API via <strong>ctypes</strong>)</dt>
<dd><ul class="first last simple">
<li>GEOS (Geometry Engine Open Source)</li>
<li>GDAL/OGR (Geospatial Data Abstraction Library)</li>
<li>PROJ.4 (Cartographic Projections Library)</li>
<li>GeoIP</li>
</ul>
</dd>
</dl>
</li>
</ul>
</div>
<div class="slide" id="geodjango-model-api-1">
<h1>GeoDjango: Model API (1)</h1>
<blockquote>
<strong>Geometry Field</strong> (django.contrib.gis.db extends django.db)</blockquote>
<ul>
<li><p class="first">PointField, LineStringField, PolygonField</p>
</li>
<li><p class="first">MultiPointField, MultiLineStringField, MultiPolygonField</p>
</li>
<li><p class="first">GeometryCollectionField</p>
</li>
<li><p class="first">GeometryField</p>
<blockquote>
<p>Geometry Field options</p>
</blockquote>
</li>
<li><p class="first"><strong>srid</strong> (default 4326 = WGS84 dd)</p>
</li>
<li><p class="first"><strong>dim</strong> (default 2, 3 will support z)</p>
</li>
<li><p class="first"><strong>spatial_index</strong> (default True, spatial index is built)</p>
</li>
</ul>
</div>
<div class="slide" id="geodjango-model-api-2">
<h1>GeoDjango: Model API (2)</h1>
<blockquote>
In Django models we get <strong>Geometry Field</strong> and <strong>GeoManager</strong></blockquote>
<div class="highlight"><pre><span class="kn">from</span> <span class="nn">django.contrib.gis.db</span> <span class="kn">import</span> <span class="n">models</span>
<span class="k">class</span> <span class="nc">Site</span><span class="p">(</span><span class="n">models</span><span class="o">.</span><span class="n">Model</span><span class="p">):</span>
<span class="sd">"""Spatial model for site"""</span>
<span class="n">code</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">IntegerField</span><span class="p">()</span>
<span class="n">name</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">CharField</span><span class="p">(</span><span class="n">max_length</span><span class="o">=</span><span class="mi">50</span><span class="p">)</span>
<span class="n">geometry</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">MultiPolygonField</span><span class="p">(</span><span class="n">srid</span><span class="o">=</span><span class="mi">4326</span><span class="p">)</span>
<span class="n">objects</span> <span class="o">=</span> <span class="n">models</span><span class="o">.</span><span class="n">GeoManager</span><span class="p">()</span>
</pre></div>
</div>
<div class="slide" id="geodjango-model-api-3">
<h1>GeoDjango: Model API (3)</h1>
<div class="highlight"><pre><span class="nv">$ </span>./manage.py sqlall myapp
</pre></div>
<div class="highlight"><pre><span class="k">BEGIN</span><span class="p">;</span>
<span class="k">CREATE</span> <span class="k">TABLE</span> <span class="ss">"myapp_site"</span> <span class="p">(</span>
<span class="ss">"id"</span> <span class="nb">serial</span> <span class="k">NOT</span> <span class="k">NULL</span> <span class="k">PRIMARY</span> <span class="k">KEY</span><span class="p">,</span>
<span class="ss">"code"</span> <span class="nb">integer</span> <span class="k">NOT</span> <span class="k">NULL</span><span class="p">,</span>
<span class="ss">"name"</span> <span class="nb">varchar</span><span class="p">(</span><span class="mi">50</span><span class="p">)</span> <span class="k">NOT</span> <span class="k">NULL</span>
<span class="p">)</span>
<span class="p">;</span>
<span class="k">SELECT</span> <span class="n">AddGeometryColumn</span><span class="p">(</span><span class="s1">'myapp_site'</span><span class="p">,</span> <span class="s1">'geometry'</span><span class="p">,</span> <span class="mi">4326</span><span class="p">,</span> <span class="s1">'MULTIPOLYGON'</span><span class="p">,</span> <span class="mi">2</span><span class="p">);</span>
<span class="k">ALTER</span> <span class="k">TABLE</span> <span class="ss">"myapp_site"</span> <span class="k">ALTER</span> <span class="ss">"geometry"</span> <span class="k">SET</span> <span class="k">NOT</span> <span class="k">NULL</span><span class="p">;</span>
<span class="k">CREATE</span> <span class="k">INDEX</span> <span class="ss">"myapp_site_geometry_id"</span>
<span class="k">ON</span> <span class="ss">"myapp_site"</span> <span class="k">USING</span> <span class="n">GIST</span> <span class="p">(</span> <span class="ss">"geometry"</span> <span class="n">GIST_GEOMETRY_OPS</span> <span class="p">);</span>
<span class="k">COMMIT</span><span class="p">;</span>
</pre></div>
</div>
<div class="slide" id="geodjango-model-api-4">
<h1>GeoDjango: Model API (4)</h1>
<blockquote>
CRUD methods: Create, Update</blockquote>
<div class="highlight"><pre><span class="o">>>></span> <span class="kn">from</span> <span class="nn">myapp.models</span> <span class="kn">import</span> <span class="o">*</span>
<span class="o">>>></span> <span class="n">new_point</span> <span class="o">=</span> <span class="n">SandboxLayer</span><span class="p">(</span><span class="n">nome</span><span class="o">=</span><span class="s">'punto 1'</span><span class="p">,</span> <span class="n">geometry</span><span class="o">=</span><span class="s">'POINT(13.8 42.5)'</span><span class="p">)</span>
<span class="o">>>></span> <span class="n">new_point</span><span class="o">.</span><span class="n">save</span><span class="p">()</span>
<span class="o">>>></span> <span class="k">print</span><span class="p">(</span><span class="n">connection</span><span class="o">.</span><span class="n">queries</span><span class="p">[</span><span class="o">-</span><span class="mi">1</span><span class="p">])</span>
<span class="p">{</span><span class="s">'time'</span><span class="p">:</span> <span class="s">'0.061'</span><span class="p">,</span> <span class="s">'sql'</span><span class="p">:</span> <span class="s">'INSERT INTO "fauna_sandboxlayer" ("nome", "geometry")</span>
<span class="n">VALUES</span> <span class="p">(</span><span class="n">E</span>\<span class="s">'punto 1</span><span class="se">\'</span><span class="s">, ST_GeomFromEWKB(E</span><span class="se">\'\\\\</span><span class="s">001</span><span class="se">\\\\</span><span class="s">...'</span><span class="p">))</span><span class="s">'}</span>
</pre></div>
<div class="highlight"><pre><span class="o">>>></span> <span class="n">new_point</span> <span class="o">=</span> <span class="n">SandboxLayer</span><span class="o">.</span><span class="n">objects</span><span class="o">.</span><span class="n">get</span><span class="p">(</span><span class="n">nome__contains</span><span class="o">=</span><span class="s">'pun'</span><span class="p">)</span>
<span class="o">>>></span> <span class="n">new_point</span><span class="o">.</span><span class="n">nome</span> <span class="o">=</span> <span class="s">'punto 2'</span>
<span class="o">>>></span> <span class="n">new_point</span><span class="o">.</span><span class="n">save</span><span class="p">()</span>
<span class="o">>>></span> <span class="k">print</span><span class="p">(</span><span class="n">connection</span><span class="o">.</span><span class="n">queries</span><span class="p">[</span><span class="o">-</span><span class="mi">1</span><span class="p">])</span>
<span class="p">{</span><span class="s">'time'</span><span class="p">:</span> <span class="s">'0.002'</span><span class="p">,</span> <span class="s">'sql'</span><span class="p">:</span> <span class="s">'UPDATE "fauna_sandboxlayer" SET "nome" = E</span><span class="se">\'</span><span class="s">punto 2</span><span class="se">\'</span><span class="s">,</span>
<span class="s">"geometry"</span> <span class="o">=</span> <span class="n">ST_GeomFromEWKB</span><span class="p">(</span><span class="n">E</span>\<span class="s">'</span><span class="se">\\\\</span><span class="s">001</span><span class="se">\\\\</span><span class="s">...'</span><span class="p">)</span>
<span class="n">WHERE</span> <span class="s">"fauna_sandboxlayer"</span><span class="o">.</span><span class="s">"id"</span> <span class="o">=</span> <span class="mi">1</span> <span class="s">'}</span>
</pre></div>
</div>
<div class="slide" id="geodjango-model-api-5">
<h1>GeoDjango: Model API (5)</h1>
<blockquote>
CRUD methods: Read, Delete</blockquote>
<div class="highlight"><pre><span class="o">>>></span> <span class="n">avvistamento</span> <span class="o">=</span> <span class="n">Avvistamento</span><span class="o">.</span><span class="n">objects</span><span class="o">.</span><span class="n">get</span><span class="p">(</span><span class="nb">id</span><span class="o">=</span><span class="mi">1</span><span class="p">)</span>
<span class="o">>>></span> <span class="n">regione</span> <span class="o">=</span> <span class="n">Regione</span><span class="o">.</span><span class="n">objects</span><span class="o">.</span><span class="n">filter</span><span class="p">(</span><span class="n">geometry__intersects</span><span class="o">=</span><span class="n">avvistamento</span><span class="o">.</span><span class="n">geometry</span><span class="p">)</span>
<span class="o">>>></span> <span class="n">regione</span>
<span class="p">[</span><span class="o"><</span><span class="n">Regione</span><span class="p">:</span> <span class="n">ABRUZZO</span><span class="o">></span><span class="p">]</span>
<span class="o">>>></span> <span class="k">print</span><span class="p">(</span><span class="n">connection</span><span class="o">.</span><span class="n">queries</span><span class="p">[</span><span class="o">-</span><span class="mi">1</span><span class="p">])</span>
<span class="p">{</span><span class="s">'time'</span><span class="p">:</span> <span class="s">'0.187'</span><span class="p">,</span> <span class="s">'sql'</span><span class="p">:</span> <span class="s">'SELECT "fauna_regione"."id", "fauna_regione"."codice",</span>
<span class="s">"fauna_regione"</span><span class="o">.</span><span class="s">"nome"</span><span class="p">,</span> <span class="s">"fauna_regione"</span><span class="o">.</span><span class="s">"geometry"</span>
<span class="n">FROM</span> <span class="s">"fauna_regione"</span> <span class="n">WHERE</span> <span class="n">ST_Intersects</span><span class="p">(</span><span class="s">"fauna_regione"</span><span class="o">.</span><span class="s">"geometry"</span><span class="p">,</span>
<span class="n">ST_GeomFromEWKB</span><span class="p">(</span><span class="n">E</span>\<span class="s">'</span><span class="se">\\\\</span><span class="s">001\...'</span><span class="p">))</span> <span class="n">LIMIT</span> <span class="mi">21</span><span class="s">'}</span>
</pre></div>
<div class="highlight"><pre><span class="o">>>></span> <span class="n">sandfeat</span> <span class="o">=</span> <span class="n">SandboxLayer</span><span class="o">.</span><span class="n">objects</span><span class="o">.</span><span class="n">get</span><span class="p">(</span><span class="nb">id</span><span class="o">=</span><span class="mi">1</span><span class="p">)</span>
<span class="o">>>></span> <span class="n">sandfeat</span><span class="o">.</span><span class="n">delete</span><span class="p">()</span>
<span class="o">>>></span> <span class="k">print</span><span class="p">(</span><span class="n">connection</span><span class="o">.</span><span class="n">queries</span><span class="p">[</span><span class="o">-</span><span class="mi">1</span><span class="p">])</span>
<span class="p">{</span><span class="s">'time'</span><span class="p">:</span> <span class="s">'0.002'</span><span class="p">,</span> <span class="s">'sql'</span><span class="p">:</span> <span class="s">'DELETE FROM "fauna_sandboxlayer" WHERE "id" IN (1)'</span><span class="p">}</span>
<span class="o">>>></span> <span class="n">SandboxLayer</span><span class="o">.</span><span class="n">objects</span><span class="o">.</span><span class="n">all</span><span class="p">()</span><span class="o">.</span><span class="n">delete</span><span class="p">()</span>
<span class="o">>>></span> <span class="k">print</span><span class="p">(</span><span class="n">connection</span><span class="o">.</span><span class="n">queries</span><span class="p">[</span><span class="o">-</span><span class="mi">2</span><span class="p">])</span>
<span class="p">{</span><span class="s">'time'</span><span class="p">:</span> <span class="s">'0.002'</span><span class="p">,</span> <span class="s">'sql'</span><span class="p">:</span> <span class="s">'DELETE FROM "fauna_sandboxlayer" WHERE "id" IN (3, 2)'</span><span class="p">}</span>
</pre></div>
</div>
<div class="slide" id="geodjango-geos-api-1">
<h1>GeoDjango: GEOS API (1)</h1>
<blockquote>
a model for geometric objects (Simple Feature Access)</blockquote>
<ul class="simple">
<li>Point</li>
<li>LineString, LinearRing</li>
<li>Polygon</li>
<li>Geometry Collections (MultiPoint, MultiLineString, MultiPolygon, GeometryCollection)</li>
</ul>
</div>
<div class="slide" id="geodjango-geos-api-2">
<h1>GeoDjango: GEOS API (2)</h1>
<ul class="simple">
<li><strong>geometric attributes and methods</strong> (empty, geom_type, num_coords, centroid, area, distance, length, srs, transform...)</li>
<li><strong>representation and interoperation</strong> (ewkt, hex, hexewkb, json, geojson, kml, ogr, wkb, ewkb, wkt)</li>
<li><strong>unary predicates</strong> (has_z, simple, valid...)</li>
<li><strong>binary predicates</strong> (contains, crosses, equals, intersects, touches, within, ...)</li>
<li><strong>constructive spatial analysis methods</strong> (buffer, difference, intersection, simplify, union, envelope, ...)</li>
</ul>
</div>
<div class="slide" id="geodjango-geos-api-example-1">
<h1>GeoDjango: GEOS API, Example 1</h1>
<blockquote>
geometric objects (point), geometric properties (hasz, geom_type)
and representation and serialization</blockquote>
<div class="highlight"><pre><span class="o">>>></span> <span class="kn">from</span> <span class="nn">myapp.models</span> <span class="kn">import</span> <span class="n">Place</span>
<span class="o">>>></span> <span class="n">place</span> <span class="o">=</span> <span class="n">Place</span><span class="o">.</span><span class="n">objects</span><span class="o">.</span><span class="n">get</span><span class="p">(</span><span class="nb">id</span><span class="o">=</span><span class="mi">1</span><span class="p">)</span>
<span class="o">>>></span> <span class="n">point</span> <span class="o">=</span> <span class="n">place</span><span class="o">.</span><span class="n">geometry</span>
<span class="o">>>></span> <span class="n">point</span><span class="o">.</span><span class="n">x</span><span class="p">,</span> <span class="n">point</span><span class="o">.</span><span class="n">y</span>
<span class="p">(</span><span class="mf">13.798828125</span><span class="p">,</span> <span class="mf">42.5390625</span><span class="p">)</span>
<span class="o">>>></span> <span class="n">point</span><span class="o">.</span><span class="n">hasz</span>
<span class="bp">False</span>
<span class="o">>>></span> <span class="n">point</span><span class="o">.</span><span class="n">geom_type</span>
<span class="s">'Point'</span>
<span class="o">>>></span> <span class="n">point</span><span class="o">.</span><span class="n">json</span>
<span class="s">'{ "type": "Point", "coordinates": [ 13.798828, 42.539062 ] }'</span>
<span class="o">>>></span> <span class="n">point</span><span class="o">.</span><span class="n">ewkt</span> <span class="c"># extended wkt</span>
<span class="s">'SRID=4326;POINT (13.7988281250000000 42.5390625000000000)'</span>
</pre></div>
</div>
<div class="slide" id="geodjango-geos-api-example-2">
<h1>GeoDjango: GEOS API, Example 2</h1>
<blockquote>
predicates and relationships, transformations (requires GDAL), spatial analysis methods</blockquote>
<div class="highlight"><pre><span class="o">>>></span> <span class="kn">from</span> <span class="nn">myapp.models</span> <span class="kn">import</span> <span class="o">*</span>
<span class="o">>>></span> <span class="n">abruzzo</span> <span class="o">=</span> <span class="n">Regione</span><span class="o">.</span><span class="n">objects</span><span class="o">.</span><span class="n">get</span><span class="p">(</span><span class="n">nome</span><span class="o">=</span><span class="s">'ABRUZZO'</span><span class="p">)</span>
<span class="o">>>></span> <span class="n">avvistamento</span> <span class="o">=</span> <span class="n">Avvistamento</span><span class="o">.</span><span class="n">objects</span><span class="o">.</span><span class="n">get</span><span class="p">(</span><span class="nb">id</span><span class="o">=</span><span class="mi">1</span><span class="p">)</span>
<span class="o">>>></span> <span class="n">abruzzo</span><span class="o">.</span><span class="n">geometry</span><span class="o">.</span><span class="n">contains</span><span class="p">(</span><span class="n">avvistamento</span><span class="o">.</span><span class="n">geometry</span><span class="p">)</span>
<span class="bp">True</span>
<span class="o">>>></span> <span class="n">avvistamento</span><span class="o">.</span><span class="n">geometry</span><span class="o">.</span><span class="n">ewkt</span>
<span class="s">'SRID=4326;POINT (13.7988281250000000 42.5390625000000000)'</span>
<span class="o">>>></span> <span class="n">transformed_point</span> <span class="o">=</span> <span class="n">avvistamento</span><span class="o">.</span><span class="n">geometry</span><span class="o">.</span><span class="n">transform</span><span class="p">(</span><span class="mi">3395</span><span class="p">,</span><span class="n">clone</span><span class="o">=</span><span class="bp">True</span><span class="p">)</span>
<span class="o">>>></span> <span class="n">transformed_point</span><span class="o">.</span><span class="n">ewkt</span>
<span class="s">'SRID=3395;POINT (1536078.5204189007636160 5213176.4834084874019027)'</span>
<span class="o">>>></span> <span class="nb">buffer</span> <span class="o">=</span> <span class="n">SandboxLayer</span><span class="p">(</span><span class="n">nome</span><span class="o">=</span><span class="s">'buffer'</span><span class="p">,</span><span class="n">geometry</span><span class="o">=</span><span class="n">transformed_point</span><span class="o">.</span><span class="n">buffer</span><span class="p">(</span><span class="mi">20000</span><span class="p">))</span>
<span class="o">>>></span> <span class="nb">buffer</span><span class="o">.</span><span class="n">save</span><span class="p">()</span>
</pre></div>
</div>
<div class="slide" id="geodjango-gdal-ogr-api">
<h1>GeoDjango: GDAL/OGR API</h1>
<blockquote>
excellent alternative to GDAL/OGR Python bindings</blockquote>
<ul class="simple">
<li>not <strong>required</strong> for GeoDjango (required only for srs trasformations and for LayerMapping)</li>
<li>via the <strong>DataSource</strong> class get the access to any <strong>OGR</strong> format, (R/W in many cases)</li>
<li>get access to the GEOS API via geos method on <strong>OGRGeometry</strong> class</li>
<li>get access to other API via interoperation and representation properties (wkt, wkb, json, ...)</li>
</ul>
</div>
<div class="slide" id="geodjango-gdal-ogr-api-example">
<h1>GeoDjango: GDAL/OGR API, Example</h1>
<div class="highlight"><pre><span class="o">>>></span> <span class="kn">from</span> <span class="nn">django.contrib.gis.gdal</span> <span class="kn">import</span> <span class="o">*</span>
<span class="o">>>></span> <span class="n">ds</span> <span class="o">=</span> <span class="n">DataSource</span><span class="p">(</span><span class="s">'data/shapefile/myshape.shp'</span><span class="p">)</span>
<span class="o">>>></span> <span class="k">print</span><span class="p">(</span><span class="n">ds</span><span class="p">)</span>
<span class="n">data</span><span class="o">/</span><span class="n">shapefile</span><span class="o">/</span><span class="n">myshape</span><span class="o">.</span><span class="n">shp</span> <span class="p">(</span><span class="n">ESRI</span> <span class="n">Shapefile</span><span class="p">)</span>
<span class="o">>>></span> <span class="k">print</span><span class="p">(</span><span class="nb">len</span><span class="p">(</span><span class="n">ds</span><span class="p">))</span>
<span class="mi">1</span>
<span class="o">>>></span> <span class="n">lyr</span> <span class="o">=</span> <span class="n">ds</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span>
<span class="o">>>></span> <span class="k">print</span><span class="p">(</span><span class="n">lyr</span><span class="p">)</span>
<span class="n">myshape</span>
<span class="o">>>></span> <span class="k">print</span><span class="p">(</span><span class="n">lyr</span><span class="o">.</span><span class="n">num_feat</span><span class="p">)</span>
<span class="mi">20</span>
<span class="o">>>></span> <span class="k">print</span><span class="p">(</span><span class="n">lyr</span><span class="o">.</span><span class="n">geom_type</span><span class="p">)</span>
<span class="n">Polygon</span>
<span class="o">>>></span> <span class="k">print</span><span class="p">(</span><span class="n">lyr</span><span class="o">.</span><span class="n">srs</span><span class="o">.</span><span class="n">srid</span><span class="p">)</span>
<span class="mi">4326</span>
</pre></div>
</div>
<div class="slide" id="id2">
<h1>GeoDjango: GDAL/OGR API, Example</h1>
<div class="highlight"><pre><span class="o">>>></span> <span class="k">print</span><span class="p">(</span><span class="n">lyr</span><span class="o">.</span><span class="n">fields</span><span class="p">)</span>
<span class="p">[</span><span class="s">'gid'</span><span class="p">,</span> <span class="s">'objectid'</span><span class="p">,</span> <span class="s">'code'</span><span class="p">,</span> <span class="s">'name'</span><span class="p">,</span> <span class="s">'shape_area'</span><span class="p">,</span> <span class="s">'shape_len'</span><span class="p">]</span>
<span class="o">>>></span> <span class="k">for</span> <span class="n">feat</span> <span class="ow">in</span> <span class="n">lyr</span><span class="p">:</span>
<span class="o">....</span><span class="p">:</span> <span class="k">print</span><span class="p">(</span><span class="n">feat</span><span class="o">.</span><span class="n">get</span><span class="p">(</span><span class="s">'name'</span><span class="p">),</span> <span class="n">feat</span><span class="o">.</span><span class="n">geom</span><span class="o">.</span><span class="n">num_points</span><span class="p">)</span>
<span class="o">....</span><span class="p">:</span>
<span class="n">first_feature</span> <span class="mi">14811</span>
<span class="n">second_feature</span> <span class="mi">3598</span>
<span class="o">...</span>
<span class="n">last_feature</span> <span class="mi">19131</span>
<span class="o">>>></span> <span class="n">feat</span> <span class="o">=</span> <span class="n">lyr</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span>
<span class="o">>>></span> <span class="k">print</span><span class="p">(</span><span class="n">feat</span><span class="o">.</span><span class="n">get</span><span class="p">(</span><span class="s">'name'</span><span class="p">))</span>
<span class="n">first_feature</span>
<span class="o">>>></span> <span class="n">geom</span> <span class="o">=</span> <span class="n">feat</span><span class="o">.</span><span class="n">geom</span> <span class="c"># OGRGeometry, non GEOSGeometry</span>
<span class="o">>>></span> <span class="k">print</span><span class="p">(</span><span class="n">geom</span><span class="o">.</span><span class="n">srid</span><span class="p">)</span>
<span class="mi">4326</span>
<span class="o">>>></span> <span class="k">print</span><span class="p">(</span><span class="n">feat</span><span class="o">.</span><span class="n">geom</span><span class="o">.</span><span class="n">wkt</span><span class="p">[:</span><span class="mi">100</span><span class="p">])</span>
<span class="n">MULTIPOLYGON</span> <span class="p">(((</span><span class="mf">8.439415832216145</span> <span class="mf">46.465900481500874</span><span class="p">,</span><span class="mf">8.439484266241374</span> <span class="mf">46.465576832714113</span><span class="p">,</span><span class="mf">8.43950386</span><span class="o">...</span>
</pre></div>
</div>
<div class="slide" id="geodjango-measurement-units-api">
<h1>GeoDjango: Measurement Units API</h1>
<blockquote>
API for measurement units conversion and management</blockquote>
<div class="highlight"><pre><span class="o">>>></span> <span class="kn">from</span> <span class="nn">django.contrib.gis.measure</span> <span class="kn">import</span> <span class="n">Distance</span>
<span class="o">>>></span> <span class="n">d1</span> <span class="o">=</span> <span class="n">Distance</span><span class="p">(</span><span class="n">km</span><span class="o">=</span><span class="mi">5</span><span class="p">)</span>
<span class="o">>>></span> <span class="k">print</span> <span class="n">d1</span>
<span class="mf">5.0</span> <span class="n">km</span>
<span class="o">>>></span> <span class="k">print</span> <span class="n">d1</span><span class="o">.</span><span class="n">mi</span>
<span class="mf">3.10685596119</span>
<span class="o">>>></span> <span class="n">d2</span> <span class="o">=</span> <span class="n">Distance</span><span class="p">(</span><span class="n">mi</span><span class="o">=</span><span class="mi">5</span><span class="p">)</span>
<span class="o">>>></span> <span class="k">print</span> <span class="n">d1</span> <span class="o">+</span> <span class="n">d2</span>
<span class="mf">13.04672</span> <span class="n">km</span>
<span class="o">>>></span> <span class="n">a</span> <span class="o">=</span> <span class="n">d1</span> <span class="o">*</span> <span class="n">d2</span>
<span class="k">print</span> <span class="n">a</span>
<span class="mf">40.2336</span> <span class="n">sq_km</span>
</pre></div>
</div>
<div class="slide" id="geodjango-resources">
<h1>GeoDjango: resources</h1>
<ul class="simple">
<li>excellent documentation: <a class="reference external" href="http://docs.djangoproject.com/en/dev/ref/contrib/gis/">http://docs.djangoproject.com/en/dev/ref/contrib/gis/</a></li>
<li>official tutorial: <a class="reference external" href="http://docs.djangoproject.com/en/dev/ref/contrib/gis/tutorial/">http://docs.djangoproject.com/en/dev/ref/contrib/gis/tutorial/</a></li>
<li>GeoDjango Basic Apps: <a class="reference external" href="http://code.google.com/p/geodjango-basic-apps/">http://code.google.com/p/geodjango-basic-apps/</a></li>
<li>Python Geospatial Development, a book from Packt: <a class="reference external" href="https://www.packtpub.com/python-geo-spatial-development/book">https://www.packtpub.com/python-geo-spatial-development/book</a></li>
<li>Justin Bronn at DjangoCon 2008: <a class="reference external" href="http://www.youtube.com/watch?v=zOaimbSe6n8">http://www.youtube.com/watch?v=zOaimbSe6n8</a></li>
<li>mailing list: <a class="reference external" href="http://groups.google.com/group/geodjango">http://groups.google.com/group/geodjango</a></li>
<li>an overview by Dane Springmeyer: <a class="reference external" href="http://www.geowebguru.com/articles/99-overview-geodjango">http://www.geowebguru.com/articles/99-overview-geodjango</a></li>
<li>workshop @ FOSS4G-IT 2010 (Lugano): <a class="reference external" href="https://github.com/capooti/geodjango-tutorial">https://github.com/capooti/geodjango-tutorial</a> (in Italian)</li>
<li>a day with GeoDjango: <a class="reference external" href="http://www.paolocorti.net/2009/04/01/a-day-with-geodjango/">http://www.paolocorti.net/2009/04/01/a-day-with-geodjango/</a></li>
</ul>
</div>
<div class="slide" id="shapely">
<h1>Shapely</h1>
<ul class="simple">
<li>it is a Python binding library to GEOS via ctypes (like the GeoDjango GEOS API)</li>
<li>aims to be <strong>general purpose</strong>, not only for GIS stuff (even if it is a loyal OGC SFA implementation)</li>
<li>excellent documentation (very nice manual)</li>
<li><strong>integration</strong>: via serialization/deserialization with standard well known formats (wkt, wkb)</li>
<li><strong>projections are not supported</strong>, so geometries must be in a unique projected srs</li>
<li>license: <strong>BSD</strong></li>
</ul>
</div>
<div class="slide" id="shapely-features-ogc-sfa-1">
<h1>Shapely features: OGC SFA (1)</h1>
<blockquote>
a model for geometric objects (Simple Feature Access)</blockquote>
<ul class="simple">
<li>Point</li>
<li>LineString, LinearRing</li>
<li>Polygon</li>
<li>Geometry Collections (MultiPoint, MultiLineString, MultiPolygon, GeometryCollection)</li>
<li><strong>Empty features, Linear Referencing</strong></li>
</ul>
</div>
<div class="slide" id="shapely-ogc-sfa-2">
<h1>Shapely: OGC SFA (2)</h1>
<ul class="simple">
<li><strong>general attributes and methods</strong> (area, bounds, length, geom_type, distance, centroid, representative_point, coords, exterior, interiors)</li>
<li><strong>representation and interoperation</strong> (ewkt, hex, hexewkb, json, geojson, kml, ogr, wkb, ewkb, wkt)</li>
<li><strong>unary predicates</strong> (has_z, is_empty, is_ring, is_simple, is_valid)</li>
<li><strong>binary predicates</strong> (contains, crosses, equals, intersects, touches, within, ...)</li>
<li><strong>constructive spatial analysis methods</strong> (buffer, difference, intersection, simplify, union, polygonize, linemerge, ...)</li>
<li><strong>diagnostics</strong> (explain_validity)</li>
</ul>
</div>
<div class="slide" id="shapely-example-1">
<h1>Shapely: Example 1</h1>
<blockquote>
geometric objects (point), general attributes and methods
and representation and interoperation</blockquote>
<div class="highlight"><pre><span class="o">>>></span> <span class="kn">from</span> <span class="nn">shapely.geometry</span> <span class="kn">import</span> <span class="n">Point</span>
<span class="o">>>></span> <span class="n">point</span> <span class="o">=</span> <span class="n">Point</span><span class="p">(</span><span class="mf">0.0</span><span class="p">,</span> <span class="mf">0.0</span><span class="p">)</span>
<span class="o">>>></span> <span class="n">point</span><span class="o">.</span><span class="n">area</span>
<span class="mf">0.0</span>
<span class="o">>>></span> <span class="n">point</span><span class="o">.</span><span class="n">bounds</span>
<span class="p">(</span><span class="mf">0.0</span><span class="p">,</span> <span class="mf">0.0</span><span class="p">,</span> <span class="mf">0.0</span><span class="p">,</span> <span class="mf">0.0</span><span class="p">)</span>
<span class="o">>>></span> <span class="n">point</span><span class="o">.</span><span class="n">x</span><span class="p">,</span> <span class="n">point</span><span class="o">.</span><span class="n">y</span>
<span class="p">(</span><span class="mf">0.0</span><span class="p">,</span> <span class="mf">0.0</span><span class="p">)</span>
<span class="o">>>></span> <span class="n">point</span><span class="o">.</span><span class="n">area</span>
<span class="mf">0.0</span>
<span class="o">>>></span> <span class="n">point</span><span class="o">.</span><span class="n">length</span>
<span class="mf">0.0</span>
<span class="o">>>></span> <span class="n">point</span><span class="o">.</span><span class="n">geom_type</span>
<span class="s">'Point'</span>
<span class="o">>>></span> <span class="n">point</span><span class="o">.</span><span class="n">wkt</span>
<span class="s">'POINT (0.0000000000000000 0.0000000000000000)'</span>
</pre></div>
</div>
<div class="slide" id="shapely-example-2">
<h1>Shapely: Example 2</h1>
<blockquote>
geometric objects (polygon), general attributes and methods
and representation and interoperation</blockquote>
<div class="highlight"><pre><span class="o">>>></span> <span class="kn">from</span> <span class="nn">shapely.geometry</span> <span class="kn">import</span> <span class="n">Polygon</span>
<span class="o">>>></span> <span class="n">polygon</span> <span class="o">=</span> <span class="n">Polygon</span><span class="p">([(</span><span class="o">-</span><span class="mi">1</span><span class="p">,</span><span class="o">-</span><span class="mi">1</span><span class="p">),</span> <span class="p">(</span><span class="o">-</span><span class="mi">1</span><span class="p">,</span><span class="mi">1</span><span class="p">),</span> <span class="p">(</span><span class="mi">0</span><span class="p">,</span><span class="mi">1</span><span class="p">),</span> <span class="p">(</span><span class="mi">0</span><span class="p">,</span><span class="o">-</span><span class="mi">1</span><span class="p">)])</span>
<span class="o">>>></span> <span class="n">polygon</span><span class="o">.</span><span class="n">area</span>
<span class="mf">2.0</span>
<span class="o">>>></span> <span class="n">polygon</span><span class="o">.</span><span class="n">length</span>
<span class="mf">6.0</span>
<span class="o">>>></span> <span class="n">polygon</span><span class="o">.</span><span class="n">bounds</span>
<span class="p">(</span><span class="o">-</span><span class="mf">1.0</span><span class="p">,</span> <span class="o">-</span><span class="mf">1.0</span><span class="p">,</span> <span class="mf">0.0</span><span class="p">,</span> <span class="mf">1.0</span><span class="p">)</span>
<span class="o">>>></span> <span class="n">polygon</span><span class="o">.</span><span class="n">geom_type</span>
<span class="s">'Polygon'</span>
<span class="o">>>></span> <span class="n">polygon</span><span class="o">.</span><span class="n">wkt</span>
<span class="s">'POLYGON ((-1.0000000000000000 -1.0000000000000000, ...</span>
<span class="o">>>></span> <span class="nb">list</span><span class="p">(</span><span class="n">polygon</span><span class="o">.</span><span class="n">exterior</span><span class="o">.</span><span class="n">coords</span><span class="p">)</span>
<span class="p">[(</span><span class="o">-</span><span class="mf">1.0</span><span class="p">,</span> <span class="o">-</span><span class="mf">1.0</span><span class="p">),</span> <span class="p">(</span><span class="o">-</span><span class="mf">1.0</span><span class="p">,</span> <span class="mf">1.0</span><span class="p">),</span> <span class="p">(</span><span class="mf">0.0</span><span class="p">,</span> <span class="mf">1.0</span><span class="p">),</span> <span class="p">(</span><span class="mf">0.0</span><span class="p">,</span> <span class="o">-</span><span class="mf">1.0</span><span class="p">),</span> <span class="p">(</span><span class="o">-</span><span class="mf">1.0</span><span class="p">,</span> <span class="o">-</span><span class="mf">1.0</span><span class="p">)]</span>
<span class="o">>>></span> <span class="nb">list</span><span class="p">(</span><span class="n">polygon</span><span class="o">.</span><span class="n">interiors</span><span class="p">)</span>
<span class="p">[]</span>
</pre></div>
</div>
<div class="slide" id="shapely-example-3">
<h1>Shapely: Example 3</h1>
<blockquote>
unary predicates, binary predicates, spatial analysis methods</blockquote>
<div class="highlight"><pre><span class="o">>>></span> <span class="n">polygon</span><span class="o">.</span><span class="n">has_z</span>
<span class="bp">False</span>
<span class="o">>>></span> <span class="n">polygon</span><span class="o">.</span><span class="n">is_empty</span>
<span class="bp">False</span>
<span class="o">>>></span> <span class="n">polygon</span><span class="o">.</span><span class="n">is_valid</span>
<span class="bp">True</span>
<span class="o">>>></span> <span class="n">polygon</span><span class="o">.</span><span class="n">contains</span><span class="p">(</span><span class="n">point</span><span class="p">)</span>
<span class="bp">False</span>
<span class="o">>>></span> <span class="nb">buffer</span> <span class="o">=</span> <span class="n">polygon</span><span class="o">.</span><span class="n">buffer</span><span class="p">(</span><span class="mi">1</span><span class="p">)</span>
<span class="o">>>></span> <span class="nb">buffer</span><span class="o">.</span><span class="n">contains</span><span class="p">(</span><span class="n">point</span><span class="p">)</span>
<span class="bp">True</span>
</pre></div>
</div>
<div class="slide" id="shapely-example-4">
<h1>Shapely: Example 4</h1>
<blockquote>
diagnostics</blockquote>
<div class="highlight"><pre><span class="o">>>></span> <span class="n">coords</span> <span class="o">=</span> <span class="p">[(</span><span class="mi">0</span><span class="p">,</span> <span class="mi">0</span><span class="p">),</span> <span class="p">(</span><span class="mi">0</span><span class="p">,</span> <span class="mi">2</span><span class="p">),</span> <span class="p">(</span><span class="mi">1</span><span class="p">,</span> <span class="mi">1</span><span class="p">),</span> <span class="p">(</span><span class="mi">2</span><span class="p">,</span> <span class="mi">2</span><span class="p">),</span> <span class="p">(</span><span class="mi">2</span><span class="p">,</span> <span class="mi">0</span><span class="p">),</span> <span class="p">(</span><span class="mi">1</span><span class="p">,</span> <span class="mi">1</span><span class="p">),</span> <span class="p">(</span><span class="mi">0</span><span class="p">,</span> <span class="mi">0</span><span class="p">)]</span>
<span class="o">>>></span> <span class="n">p</span> <span class="o">=</span> <span class="n">Polygon</span><span class="p">(</span><span class="n">coords</span><span class="p">)</span>
<span class="o">>>></span> <span class="kn">from</span> <span class="nn">shapely.validation</span> <span class="kn">import</span> <span class="n">explain_validity</span>
<span class="o">>>></span> <span class="n">explain_validity</span><span class="p">(</span><span class="n">p</span><span class="p">)</span>
<span class="s">'Ring Self-intersection[1 1]'</span>
</pre></div>
</div>
<div class="slide" id="shapely-resources">
<h1>Shapely: resources</h1>
<ul class="simple">
<li>excellent documentation: <a class="reference external" href="http://gispython.org/shapely/docs/1.2/">http://gispython.org/shapely/docs/1.2/</a></li>
<li>GIS Python Lab: <a class="reference external" href="http://trac.gispython.org/lab">http://trac.gispython.org/lab</a></li>
<li>Sean Gillies Blog: <a class="reference external" href="http://sgillies.net/blog/">http://sgillies.net/blog/</a></li>
<li>Python Workshop at FOSS4G 2010: <a class="reference external" href="http://www.mapfish.org/doc/tutorials/python-workshop/geoalchemy.html">http://www.mapfish.org/doc/tutorials/python-workshop/geoalchemy.html</a></li>
<li>mailing list @gispython.org: <a class="reference external" href="http://lists.gispython.org/mailman/listinfo/community">http://lists.gispython.org/mailman/listinfo/community</a></li>
</ul>
</div>
<div class="slide" id="geoalchemy">
<h1>GeoAlchemy</h1>
<blockquote>
GeoAlchemy</blockquote>
<ul class="simple">
<li>it is a spatial extension to <strong>SQLAlchemy</strong></li>
<li>it provides support for Geospatial data types at the ORM layer using SQLAlchemy</li>
<li>it aims to support spatial operations and relations specified by the Open Geospatial Consortium (OGC). The project started under Google Summer of Code Program</li>
<li>differently from other libraries, it does <strong>NOT DEPEND</strong> on other GIS building blocks (GDAL, GEOS...)</li>
<li>still not so mature like GeoDjango</li>
<li>license: <strong>MIT</strong></li>
</ul>
</div>
<div class="slide" id="geoalchemy-sqlalchemy-notes">
<h1>GeoAlchemy: SQLAlchemy notes</h1>
<blockquote>
SQLAlchemy</blockquote>
<ul class="simple">
<li>SQLAlchemy is the most powerful Python SQL Toolkit and ORM</li>
<li>compared to the Django ORM, it has a most powerfull abstraction</li>
<li>supports not only tables (like Django) but also <strong>joins, subqueries, and unions</strong></li>
<li>higly <strong>scalable</strong> (ie: configuration of how many SELECT to emit while loading whole graphs of objects: lazy loading and eager load)</li>
<li>greater set of DB supported if compared to Django</li>
<li>support for <strong>transactions</strong> (i.e. nice rollback mechanism)</li>
<li>excellent documentations</li>
</ul>
</div>
<div class="slide" id="geoalchemy-spatial-database">
<h1>GeoAlchemy: Spatial database</h1>
<blockquote>
Supported spatial database</blockquote>
<ul class="simple">
<li>PostGis</li>
<li>Spatialite</li>
<li>MySQL (not OGC-compliant, limited functionality)</li>
<li>Oracle</li>
<li>MS SQL Server 2008 (Django does not support it)</li>
</ul>
</div>
<div class="slide" id="geoalchemy-use-cases">
<h1>GeoAlchemy: Use cases</h1>
<ul class="simple">
<li>like Django, you may use it in <strong>desktop and web</strong> application</li>
<li>web frameworks that integrates well with SQLAlchemy: TurboGears and Pylons (highly configurable for models, templates and helpers)</li>
<li>Django is not the best SQLAlchemy friend, but you may still use it :D</li>
</ul>
</div>
<div class="slide" id="geoalchemy-features">
<h1>GeoAlchemy: features</h1>
<ul class="simple">
<li><strong>NO</strong> model for geometric objects (Simple Feature Access) :(</li>
<li><strong>geometric attributes and methods</strong> (dimension, srid, geometry_type, num_points, length, area, centroid, transform, coords)</li>
<li><strong>representation and interoperation</strong> (wkt, wkb, svg, gml, kml, geojson)</li>
<li><strong>unary predicates</strong> (has_z, is_valid, is_empty, is_simple, is_closed, is_ring)</li>
<li><strong>binary predicates</strong> (contains, crosses, equals, intersects, touches, within, ...)</li>
<li><strong>constructive spatial analysis methods</strong> [limited] (buffer, boundary, convex_hull)</li>
</ul>
</div>
<div class="slide" id="geoalchemy-example-1">
<h1>GeoAlchemy: Example 1</h1>
<blockquote>
the model</blockquote>
<div class="highlight"><pre><span class="n">engine</span> <span class="o">=</span> <span class="n">create_engine</span><span class="p">(</span><span class="s">'postgresql://postgres:postgres@localhost/gis_test'</span><span class="p">,</span> <span class="n">echo</span><span class="o">=</span><span class="bp">True</span><span class="p">)</span>
<span class="n">Session</span> <span class="o">=</span> <span class="n">sessionmaker</span><span class="p">(</span><span class="n">bind</span><span class="o">=</span><span class="n">engine</span><span class="p">)</span>
<span class="n">session</span> <span class="o">=</span> <span class="n">Session</span><span class="p">()</span>
<span class="n">metadata</span> <span class="o">=</span> <span class="n">MetaData</span><span class="p">(</span><span class="n">engine</span><span class="p">)</span>
<span class="n">Base</span> <span class="o">=</span> <span class="n">declarative_base</span><span class="p">(</span><span class="n">metadata</span><span class="o">=</span><span class="n">metadata</span><span class="p">)</span>
<span class="k">class</span> <span class="nc">Spot</span><span class="p">(</span><span class="n">Base</span><span class="p">):</span>
<span class="n">__tablename__</span> <span class="o">=</span> <span class="s">'spots'</span>
<span class="nb">id</span> <span class="o">=</span> <span class="n">Column</span><span class="p">(</span><span class="n">Integer</span><span class="p">,</span> <span class="n">primary_key</span><span class="o">=</span><span class="bp">True</span><span class="p">)</span>
<span class="n">name</span> <span class="o">=</span> <span class="n">Column</span><span class="p">(</span><span class="n">Unicode</span><span class="p">,</span> <span class="n">nullable</span><span class="o">=</span><span class="bp">False</span><span class="p">)</span>
<span class="n">height</span> <span class="o">=</span> <span class="n">Column</span><span class="p">(</span><span class="n">Integer</span><span class="p">)</span>
<span class="n">created</span> <span class="o">=</span> <span class="n">Column</span><span class="p">(</span><span class="n">DateTime</span><span class="p">,</span> <span class="n">default</span><span class="o">=</span><span class="n">datetime</span><span class="o">.</span><span class="n">now</span><span class="p">())</span>
<span class="n">geom</span> <span class="o">=</span> <span class="n">GeometryColumn</span><span class="p">(</span><span class="n">Point</span><span class="p">(</span><span class="mi">2</span><span class="p">))</span>
<span class="n">metadata</span><span class="o">.</span><span class="n">drop_all</span><span class="p">()</span> <span class="c"># comment this on first occassion</span>
<span class="n">metadata</span><span class="o">.</span><span class="n">create_all</span><span class="p">()</span>
</pre></div>
</div>
<div class="slide" id="geoalchemy-example-2">
<h1>GeoAlchemy: Example 2</h1>
<blockquote>
data creation</blockquote>
<div class="highlight"><pre><span class="o">>>></span> <span class="n">wkt_spot1</span> <span class="o">=</span> <span class="s">"POINT(-81.40 38.08)"</span>
<span class="o">>>></span> <span class="n">spot1</span> <span class="o">=</span> <span class="n">Spot</span><span class="p">(</span><span class="n">name</span><span class="o">=</span><span class="s">"Gas Station"</span><span class="p">,</span> <span class="n">height</span><span class="o">=</span><span class="mf">240.8</span><span class="p">,</span> <span class="n">geom</span><span class="o">=</span><span class="n">WKTSpatialElement</span><span class="p">(</span><span class="n">wkt_spot1</span><span class="p">))</span>
<span class="o">>>></span> <span class="n">geom_spot2</span> <span class="o">=</span> <span class="n">WKTSpatialElement</span><span class="p">(</span><span class="s">'POINT(30250865 -610981)'</span><span class="p">,</span> <span class="mi">2249</span><span class="p">)</span>
<span class="o">>>></span> <span class="n">spot2</span> <span class="o">=</span> <span class="n">Spot</span><span class="p">(</span><span class="n">name</span><span class="o">=</span><span class="s">"Park"</span><span class="p">,</span> <span class="n">height</span><span class="o">=</span><span class="mf">53.2</span><span class="p">,</span> <span class="n">geom</span><span class="o">=</span><span class="n">geom_spot2</span>
<span class="o">>>></span> <span class="n">session</span><span class="o">.</span><span class="n">add_all</span><span class="p">([</span><span class="n">spot1</span><span class="p">,</span> <span class="n">spot2</span><span class="p">])</span>
<span class="o">>>></span> <span class="n">session</span><span class="o">.</span><span class="n">commit</span><span class="p">()</span>
</pre></div>
</div>
<div class="slide" id="geoalchemy-example-3">
<h1>GeoAlchemy: Example 3</h1>
<blockquote>
data reading and representation</blockquote>
<div class="highlight"><pre><span class="o">>>></span> <span class="n">s</span> <span class="o">=</span> <span class="n">session</span><span class="o">.</span><span class="n">query</span><span class="p">(</span><span class="n">Spot</span><span class="p">)</span><span class="o">.</span><span class="n">get</span><span class="p">(</span><span class="mi">1</span><span class="p">)</span>
<span class="o">>>></span> <span class="n">session</span><span class="o">.</span><span class="n">scalar</span><span class="p">(</span><span class="n">s</span><span class="o">.</span><span class="n">geom</span><span class="o">.</span><span class="n">wkt</span><span class="p">)</span>
<span class="s">'POINT(-81.42 37.65)'</span>
<span class="o">>>></span> <span class="n">session</span><span class="o">.</span><span class="n">scalar</span><span class="p">(</span><span class="n">s</span><span class="o">.</span><span class="n">geom</span><span class="o">.</span><span class="n">gml</span><span class="p">)</span>
<span class="s">'<gml:Point srsName="EPSG:4326"><gml:coordinates>-81.42,37.65</gml:coordinates></gml:Point>'</span>
<span class="o">>>></span> <span class="n">session</span><span class="o">.</span><span class="n">scalar</span><span class="p">(</span><span class="n">s</span><span class="o">.</span><span class="n">geom</span><span class="o">.</span><span class="n">kml</span><span class="p">)</span>
<span class="s">'<Point><coordinates>-81.42,37.65</coordinates></Point>'</span>
</pre></div>
</div>
<div class="slide" id="geoalchemy-example-4">
<h1>GeoAlchemy: Example 4</h1>
<blockquote>
geometric properties</blockquote>
<div class="highlight"><pre><span class="o">>>></span> <span class="n">s</span> <span class="o">=</span> <span class="n">session</span><span class="o">.</span><span class="n">query</span><span class="p">(</span><span class="n">Spot</span><span class="p">)</span><span class="o">.</span><span class="n">filter</span><span class="p">(</span><span class="n">Spot</span><span class="o">.</span><span class="n">height</span> <span class="o">></span> <span class="mi">240</span><span class="p">)</span><span class="o">.</span><span class="n">first</span><span class="p">()</span>
<span class="o">>>></span> <span class="n">session</span><span class="o">.</span><span class="n">scalar</span><span class="p">(</span><span class="n">s</span><span class="o">.</span><span class="n">geom</span><span class="o">.</span><span class="n">geometry_type</span><span class="p">)</span>
<span class="s">'ST_Point'</span>
<span class="o">>>></span> <span class="n">session</span><span class="o">.</span><span class="n">scalar</span><span class="p">(</span><span class="n">s</span><span class="o">.</span><span class="n">geom</span><span class="o">.</span><span class="n">x</span><span class="p">)</span>
<span class="o">-</span><span class="mf">81.420000000000002</span>
<span class="o">>>></span> <span class="n">session</span><span class="o">.</span><span class="n">scalar</span><span class="p">(</span><span class="n">s</span><span class="o">.</span><span class="n">geom</span><span class="o">.</span><span class="n">y</span><span class="p">)</span>
<span class="mf">37.649999999999999</span>
<span class="o">>>></span> <span class="n">s</span><span class="o">.</span><span class="n">geom</span><span class="o">.</span><span class="n">coords</span><span class="p">(</span><span class="n">session</span><span class="p">)</span>
<span class="p">[</span><span class="o">-</span><span class="mf">81.420000000000002</span><span class="p">,</span> <span class="mf">37.649999999999999</span><span class="p">]</span>
</pre></div>
</div>
<div class="slide" id="geoalchemy-example-5">
<h1>GeoAlchemy: Example 5</h1>
<blockquote>
constructive spatial analysis methods and binary predicates</blockquote>
<div class="highlight"><pre><span class="o">>>></span> <span class="n">r</span> <span class="o">=</span> <span class="n">session</span><span class="o">.</span><span class="n">query</span><span class="p">(</span><span class="n">Road</span><span class="p">)</span><span class="o">.</span><span class="n">first</span><span class="p">()</span>
<span class="o">>>></span> <span class="n">l</span> <span class="o">=</span> <span class="n">session</span><span class="o">.</span><span class="n">query</span><span class="p">(</span><span class="n">Lake</span><span class="p">)</span><span class="o">.</span><span class="n">first</span><span class="p">()</span>
<span class="o">>>></span> <span class="n">buffer_geom</span> <span class="o">=</span> <span class="n">DBSpatialElement</span><span class="p">(</span><span class="n">session</span><span class="o">.</span><span class="n">scalar</span><span class="p">(</span><span class="n">r</span><span class="o">.</span><span class="n">geom</span><span class="o">.</span><span class="n">buffer</span><span class="p">(</span><span class="mf">10.0</span><span class="p">)))</span>
<span class="o">>>></span> <span class="n">session</span><span class="o">.</span><span class="n">scalar</span><span class="p">(</span><span class="n">buffer_geom</span><span class="o">.</span><span class="n">wkt</span><span class="p">)</span>
<span class="s">'POLYGON((-77.4495270615657 28.6622373442108,....</span>
<span class="o">>>></span> <span class="n">session</span><span class="o">.</span><span class="n">query</span><span class="p">(</span><span class="n">Road</span><span class="p">)</span><span class="o">.</span><span class="n">filter</span><span class="p">(</span><span class="n">Road</span><span class="o">.</span><span class="n">geom</span><span class="o">.</span><span class="n">intersects</span><span class="p">(</span><span class="n">r</span><span class="o">.</span><span class="n">geom</span><span class="p">))</span><span class="o">.</span><span class="n">count</span><span class="p">()</span>
<span class="il">1L</span>
<span class="o">>>></span> <span class="n">session</span><span class="o">.</span><span class="n">query</span><span class="p">(</span><span class="n">Lake</span><span class="p">)</span><span class="o">.</span><span class="n">filter</span><span class="p">(</span><span class="n">Lake</span><span class="o">.</span><span class="n">geom</span><span class="o">.</span><span class="n">touches</span><span class="p">(</span><span class="n">r</span><span class="o">.</span><span class="n">geom</span><span class="p">))</span><span class="o">.</span><span class="n">count</span><span class="p">()</span>
<span class="il">0L</span>