Nginx PHP

By default, Nginx and PHP5 allow POST 2M. It's to small. Some Map.png are larger than 2M.

Nginx

In file /etc/nginx/nginx.conf, add this line:

http {
...
client_max_body_size 20M;
...
}

PHP

Modify your php.ini file :

memory_limit = 32M
upload_max_filesize = 20M
post_max_size = 20M

Edit :

Change 20M by the size you want. Some map.png files are greater than 20M. Prefer 30M.