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RTK Mapping 8
In the Asset Surveyor software, the precision settings are set in the
RTK precision options form. To open this form, pressRin the
Position filters form.
During the RTK data collection process, the precision estimate values
are constantly displayed and updated in terms of a position’s
horizontal and vertical components. You can also log the precision
estimates (QA/QC) associated with each position using the Log
QA/QC functionality.
In the Asset Surveyor software, the Log QA/QC field is found in the
Logging options form, accessed from Configuration / GPS rover
options.
The Asset Surveyor software is set by default to log precision
estimates if available. The precision values for a position can be
queried in the GPS Pathfinder Office software and can also be
exported as attributes for point features and Not in Feature positions.
While these values provide a very good indication of the quality of the
GPS signal and the computed position’s precision, they should not be
used in isolation when considering a position’s accuracy.
Calibrating to existing control points
To achieve maximum possible accuracy, it is important to search
survey records for horizontal and vertical control points that may be
used to provide a control framework for a local site calibration.
Trimble recommends that you contact a practising surveyor or survey
company for reliable information related to the control points.
Differences can exist between GPS positions and positions that have
been surveyed using conventional means, such as a theodolite and
EDM. These differences are commonplace and occur because GPS
positions are referenced to a mathematical representation of the earth
(called an ellipsoid), while conventionally surveyed positions are
referenced to a gravitational model of the earth (called a geoid). The
ellipsoid surface is very smooth and regular, while the geoid surface is
uneven, as illustrated by Figure 8.2.
TSC1 Asset Surveyor Operation Manual 193