Edit Coordinate System LatLon

View and/or edit a coordinate system latlon. A coordinate system latlon defines the LatLon-coordinates in your maps, and optionally the projection of the maps. Coordinate systems are used by polygon, segment and point maps, and by the georeference of a raster map.

This dialog box appears:

when in the Create Coordinate System dialog box, you selected to create a coordinate system of the type latlon,
when in the Catalog, you double-click a coordinate system of the type latlon,
when in the Catalog, you press the right mouse button on a coordinate system of the type latlon, and choose Open from the context-sensitive menu.

You should use a coordinate system of the type latlon, when you obtained raster maps and/or vector maps from other sources which are supposed to be using geographic coordinates (Latitude, Longitude), but when the maps do not yet have a coordinate system.

When you want to have LatLon-coordinates for maps which comprise the whole world or when are not interested in choosing an ellipsoid or datum, you can directly link system coordinate system LatLon to the maps. Edit the properties of the maps and select system coordinate system LatLon.
When you may want to change the figure used for the radius of the earth or when you may want to add ellipsoid or datum information, you can create a user-defined coordinate system of the type latlon and edit it in this dialog box.

Specify the LatLon-boundaries of the map, and optionally supply ellipsoid or datum information. You can specify ellipsoid or datum information later on or right away. When a map has ellipsoid or datum information, you will be able to transform the map to another coordinate system with another ellipsoid or another datum.

Dialog box options:

Description:	Type a description for the coordinate system. The description is visible on the status bar of the Main window when moving the mouse pointer over the coordinate system in the Catalog.
Min Latitude:	Type the minimum latitude of your map in degrees, minutes and seconds, and type S when this corner of the map in located on the southern hemisphere or type N when this corner of the map in located on the northern hemisphere.
Max Latitude:	Type the minimum latitude of your map in degrees, minutes and seconds, and type S when this corner of the map in located on the southern hemisphere or type N when this corner of the map in located on the northern hemisphere.
Min Longitude:	Type the minimum longitude of your map in degrees, minutes and seconds, and type E when this corner of the map in located on the Eastern hemisphere or type W when this corner of the map in located on the western hemisphere.
Max Longitude:	Type the maximum longitude of your map in degrees, minutes and seconds, and type E when this corner of the map in located on the eastern hemisphere or type W when this corner of the map in located on the western hemisphere.
	The boundary values will only be used to determine: default map coordinate boundaries for vector maps, and default coordinate boundaries for a georeference for raster maps.
Ellipsoid:	Click the Ellipsoid button when you want to specify an ellipsoid for the LatLon-coordinates of this coordinate system. The Select Ellipsoid dialog box will appear. You need to select an ellipsoid when you are making maps at medium scale, for instance when mapping areas like countries or provinces.
Datum:	Click the Datum button when you want to specify datum information for the LatLon-coordinates of this coordinate system. The Select Datum dialog box will appear. You need to specify a datum when you are making maps at a rather large scale (e.g. 1: 20,000 or less), thus when mapping areas like small provinces, towns, infrastructure as sewage systems, water pipes, electricity cables, etc. By supplying a datum, you will be able to transform coordinates from one datum to another; differences between ellipsoid centers will be taken into account.
Sphere radius (m):	This option is only available when no ellipsoid or datum has been selected. That is correct when mapping the entire earth, a hemisphere or larger continents. It is assumed that the earth is a sphere and a spherical model can be used. As default a sphere of 6371007.0m is given. If you wish you can change this value. In case you already selected an ellipsoid or datum, the radius (equatorial and polar) of the ellipsoid is already defined; then, the name of the selected ellipsoid and/or datum will be displayed.

Tip:

When finished creating a coordinate system latlon, you have to link this coordinate system to the maps which should use it by editing the properties of these maps.