Web Mapping Illustrated

Map Projection Examples

The examples in the following section are based on some global map data that is stored in the Geographic Coordinate System. Each example is one projection at a suitable scale. This section is intended to introduce a few of the more common types of map projections and provide a picture of what they look like. Some brief description is provided, but other books and documents are recommended for learning more about these projections.

The specific MapServer projection settings are included for reference. As long as all your layers have a valid projection set for them, these example projection settings can be used to change the output map projection.

Warning

A global map grid shapefile was used as a layer for the map figures in this section. This shapefile was used instead of the internal MapServer graticule generator (the GRID object). The GRID object produces very simple lines that can't be properly transformed by many projections.

A Python script called mkgraticule.py is included in the pymod folder of the FWTools package. This created the map grid for these maps.

For more on FWTools, see http://fwtools.maptools.org/.

Simple Cylindrical Projection

Figure A-6 shows the most basic world map. The global coordinates, latitudes, and longitudes are displayed on a rectangular grid. Each rectangle is the same size on both x and y planes. This is the default projection used with MapServer when you specify the latlong projection. It is commonly known as a Simple Cylindrical ...