80 DG14 and DG16 Board & Sensor Reference Manual
Table 5.1 provides an overview of user coordinate transformation functions for your
receiver.
The remainder of this chapter describes in more detail the coordinate
transformation features of your receiver.
The receiver normally computes and outputs positions in the WGS-84 coordinate
reference frame. However, it is possible to output positions in NMEA messages in
a number of different pre-defined datums, as well as in a user-defined datum.
To set the receiver to output positions in a different datum, use the $PASHS,DTM
command. Once set to a different datum, then all position outputs in NMEA
messages such as GGA and GLL are referenced to the chosen datum. For a list
of Datums, see Table 6.15, “Predefined Datums and Associated Reference
Ellipsoids,” on page 106.
If the list of datums does not include a datum of interest to you, you can define a
datum and load it on the receiver, using the $PASHS,UDD command along with
the $PASHS,DTM command. Prior to using these commands, define the required
parameters including the length of the semi-major axis and amount of flattening in
the reference ellipsoid, and the translation, rotation, and scale between the user-
defined system and WGS-84.
Table 5.1. User Coordinate Transformation Functionalities
Transformation Description
Datum to Datum 3D (7-parameter) datum transformation between two Cartesian XYZ
systems associated with the WGS-84 datum and local datum defined
by the user.
Datum to Grid Data projected from a geodetic system, associated with WGS-84 or a
user-defined datum and a specified grid system.
Map Projections Supported
• Mercator (EMER)
• Transverse Mercator (TM83)
• Oblique Mercator (OM83)
• Stereographic (Polar and Oblique) (STER)
• Lambert Conformal Conic (2 standard parallels) (LC83)
Special Map Projections Specific to NAD27
• Transverse Mercator 27 (TM27 and TMA7)
• Oblique Mercator 27 (OM83)
• Lambert Conformal Conic 27 (LC27)
Elevation Modeling Interpolation of geoidal undulations
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