Changing the Coordinate System

The coordinate reference system (CRS) for the map data can be changed using the Map/Change CRS menu item. An incorrect CRS will cause location markers to be displayed in the wrong places. In some cases these differences may be subtle, and identification of an incorrect CRS may require close examination of the map and reference to other descriptions or depictions of the locations.

In some cases the coordinate values in the data file may be so imcompatible with the selected (or default) CRS that the data cannot be displayed. If this is the case, mapdata may either issue an error message or, possibly, crash.

The Map/Change CRS menu item will present the following dialog.

This dialog prompts for a new CRS identifier. After a new CRS value is selected, mapdata.py converts all the latitude and longitude coordinates in the data file to the newly selected CRS and re-displays the map.

mapdata.py does not provide a list of all of the possible CRS values that may be used. External metadata may need to be consulted to identify the correct CRS for each data set.