Specifications

Coordinate Transformation 67
Coordinate
Datum to Grid
This transformation is used to generate coordinates in an <x,y> rectangular system,
based on the user’s location and mapping requirements or local standard. The user
may select any projection along with any base datum for output.
The previous section described how to set up the receiver to compute geodetic
coordinates (Latitude and Longitude) in the datum that you desire. You now have the
option to convert these geodetic coordinates into grid coordinates. This is
accomplished by defining the grid system of interest utilizing one of the projection
types available. The supported projection types are diagrammed in Figures 5.2 - 5.6
below.
To set the receiver to supply grid coordinates, you must first select the projection type
that best fits your needs. Next, you must define the grid system, using this projection
type, with the $PASHS,UDG command. This command defines the grid system to be
used. Once defined, this grid system is enabled by using the $PASHS,GRD,UDG
command. At this time, the receiver is computing grid coordinates in the system
defined. To access these grid coordinates, use either the $PASHQ,GDC command to
query for one output of the current coordinates, or use the $PASHS,NME,GDC
command to set the receiver to continuously output the current coordinates.
There is one exception to the configuration of the receiver to compute and output grid
coordinates. If you are interested in computing and outputting WGS84 based UTM
coordinates, there is no need to define the grid system in the receiver. The parameters
for WGS84 UTM are pre-set in the receiver. To use them, simply set the receiver to
output grid coordinates using either the $PASHQ,UTM command to query for one
output of the current coordinates, or use the $PASHS,NME,UTM command to set the
receiver to continuously output the current coordinates.
Check the GDC message for the currently assigned Datum.
CAUTION
Some projections and combinations of datums and projections are invalid,
even if mathematically possible.