Spectra Precision ProMark 800 Reference Manual - Manual (Page 83)

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Precise Surveying - Field Applications & Concepts
points or more is highly recommended to achieve accurate
localization on the horizontal plane. This number should
be raised up to four, or more, to ensure vertical
localization.
• Rigid Body: Same as plane similarity except that the scale
factor is held fixed throughout the localization process.
• Helmert: With this method, the user provides the seven
parameters modifying the projection system currently
used in the job. These parameters (dX, dY, dZ, rot X, rot Y,
rot Z and scale factor) may be the result of a multi-point
localization performed earlier.
• One-Point Azimuth: This method is used when only one
reference point is available to determine the local grid. In
this case, the user should specify the orientation of the
North direction of the local grid (geographic or true).
A typical application of this method is to use the point
where the base is installed at the origin (0, 0, 0), or on a
singular point (e.g. 100, 1000, 0) of the local grid. In this
case, the geographic coordinates of the base position may
feature only several meter accuracy since the surveyor is
only interested in collecting local coordinates for the job.
It will therefore be the surveyor’s responsibility to make
sure the geographic coordinates of the base (typically
determined through the autonomous GPS mode) can be
fed into the localization process.
A geoid model can be included in the localization process. In
this case, all elevations provided for the reference points used
should be orthometric instead of ellipsoidal.
Typical
Instructions to
Complete a
Localization
Process
Localization based on the use of reference points is typically
achieved through the following steps:
1. Make sure the right projection system is selected in your
job. What does that mean? Here are the two cases to
consider:
• Some reference points that you will hold horizontally or
vertically fixed in the localization process may have
their coordinates expressed in a known projection
system. We recommend you select this projection as
the job’s initial projection system.
• If the local coordinates of your reference points do not
refer to any known projection system, then we
recommend you choose a projection system that is
standard in your working area.
2. Enter the local coordinates of the first reference point.