Mapping Hacks

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Chapter 8, Building the Geospatial Web

#91 Build Interactive Web-Based Map Applications

HACK

You can also include that URL in your web pages as an image:

<img src="/cgi-bin/mapserv?map=/var/www/html/mini.map&mode=map">

The map=/var/www/html/mini.map parameter points to the map file that

describes how the map will be generated. The second parameter,

mode=map,

causes MapServer to return an image file directly.

Arguably, allowing the user to set the full path to the map

file in the URL might constitute a security breach on some

systems. One way around having to allow this is to create a

shell script that hardcodes the map file in the shell environ-

ment before executing mapserv:

#!/bin/sh

export MS_MAPFILE=/var/www/html/mini.map

exec /var/www/cgi-bin/mapserv

Having done this, you can place that shell script in your cgi-

bin directory, and use it instead of using mapserv directly, in

which case you will no longer need to provide a

map= option

through the MapServer URL.

Adding Interactivity

Generating an image from passed parameters is just the tip of the map. You

can also create a full layer-based interactive map viewer with just a bit more

effort.

For this example, we’ll use a shapefile of local roads in Allegheny County,

available from http://www.pasda.psu.edu. The specific URL of the file is ftp://

pasda.cac.psu.edu/pub/pasda/padot/local/padot-locroads-allegheny_2001.zip.

Figure 8-10. The United States, ...