STAR*NET V6 - Circe

Chapter 10 Adjustments in Grid Coordinate Systems
10.10 Entering Data for Grid System Adjustments
Remember that in a “Grid” coordinate system adjustment, you are normally supplying
field observations in a ground-surface system that will be reduced to fit your supplied
coordinates, which are in a grid system.
All station coordinates must be supplied as grid values in the form of either coordinates
or geodetic positions (latitudes and longitudes). You cannot combine “grid” and arbitrary
“local” coordinates in the same adjustment.
Input data for a grid coordinate system adjustment is prepared and entered the same way
as for a local coordinate system, except for the following differences:
1. Entered station coordinates must be grid coordinates or geodetic positions.
2. Entered station heights are normally supplied as orthometric elevations. Although
ellipsoid heights may be entered, the “standard” STAR*NET edition is designed to
handle “terrestrial” adjustments using elevation-based observations.
In the “Professional” STAR*NET edition, however, station heights are sometimes
supplied as ellipsoid heights because of the GPS vector handling facilities. To derive
orthometric elevations from these ellipsoid heights, accurate geoid heights are
provided for every station, or geoid modeling is performed.
3. By default, bearings or azimuths are entered as grid values.
But if you want to enter geodetic (or observed) bearings or azimuths, use the
“.MEASURED” inline option to change the input mode. The program internally
converts these values to grid by computing and applying proper corrections.
4. By default, all other input data, the angle and distance observations, are entered as
observed surface measurements. These observations are internally reduced to the
grid plane values during the adjustment.
But if you want to enter angle and distance values that have already been reduced to
grid (information taken from a map for example), use the “.GRID” inline option to
change the input mode. Corrections will not be computed for these values.
Descriptions of the “.MEASURED” and “.GRID” inline option data modes mentioned
above are fully detailed in Chapter 4, “Options” on page 85.
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