Purpose:
This technical note explains Grid-to-ground projections (AKA “ground coordinates”, “surface coordinates”, “localized coordinate networks”, etc.) within GeoCue. A ground coordinate system is a local coordinate system created by modifying the origin and scale of an existing projected coordinate system, such as a state plane or UTM grid system. The ground system is tied to the grid system at the specified origin (specified in grid system coordinates) and scale corrections are applied. Ground measurements will more closely match measurements in this local system than in the standard grid system on which it is based. However, scale distortions will increase as the distance from the local origin increase, and with changes in elevation.
In order to define a ground coordinate system the user needs to know:
- ground-to-grid scale factor (If the scale factor represents the grid-to-ground instead, make sure to take the reciprocal before entering the information in the GeoCue dialog)
- a local origin for the ground system (easting/northing) in the selected state plane coordinate system
- optionally, an additional false easting/northing pair to “add” at the end
Introduction. 2
Identifying the scale and shift values. 2
Specifying the Ground System.. 2
Tips to keep in mind. 4
Read the complete article: CueTip – Ground Coordinate Systems
