The Georeferencing Editor (or GeoEdit control) is a standard CATALYST Professional tool for viewing and editing the georeferencing system, bounds, and projection definition for data layers.
The GeoEdit control comes in two forms. The first is the minimal form and contains only the controls for setting the georeferencing system (for example, UTM, Long/Lat), while the second form also includes the georeferenced bounds of the region being described. Both forms allow you to view and edit the projection definition.
The GeoEdit control has two modes. In some places it is used in "Informational Only" mode where none of the values may be changed. Normally it is in "User Controlled (affects loading)" mode, which allows you to change any of the values interactively.
The georeferencing coordinate system is set by selecting the desired coordinate system from the list of possible systems. The currently available coordinate systems are:
To the right of the coordinate system list is the Earth Model button. Clicking the Earth Model button displays a window with a list of the supported datums and ellipsoids. After you choose the desired datum or ellipsoid and then click the Accept button, the window closes and the georeferencing string is updated with the Earth model selected.
To the right of the Earth Model button is a text field that contains the full georeferencing string currently in use. This includes the georeferencing coordinate system set in the coordinate system list, plus a zone number and Earth model where applicable.
The georeferencing string can be entered in the text field or can be generated from the selected georeference system, zone, and Earth model.
The zone number is placed after the georeferencing system, and before the Earth model. The Earth model appears at the end of the georeferencing string, and is indicated by a numeric code such as "E000" (Clark 1866 / NAD27) or "E012" (WGS 1984). The default Earth model is "D000" (WGS 1984).
Each time the georeferencing string changes, it is validated and reformatted. Changing the georeferencing system from one projection to another will not cause the bounding rectangle to be reprojected. Instead, the corner values will be reinterpreted in the new georeferencing system.
The projections listed in the coordinate system list are those for whom the georeferencing string defines all the parameters required for the projection. For example:
"UTM 11 E012'' "SPCS 1101 E000'' "LONG/LAT E008''
Other projections require more than a zone and Earth model to define the projection. When Other is selected from the list, a window with a list of supported projections appears. After selecting the desired projection from the list and clicking the Accept button, the Projection Definition window is displayed, which allows you to enter the parameters required for the projection. Fields not required for the projection are not active. See Projection definition for more information.
To the right of the georeferencing text field is the More button. The button is unavailable for georeference systems with no projection information (for example, pixel). When you click the More button, a window showing the existing projection definition appears. If the projection is UTM or SPCS, clicking the More button displays the appropriate Zones window.
When using a GeoEdit control to define a region, you will see five additional text fields. The two Upper Left fields define the horizontal and vertical position of the top-left corner of the region. The two Lower Right fields define the lower-right corner of the region being defined.
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