StarNet v6 manual - Engineering Surveyor

Special Options
Chapter 4 Options
This dialog is used to set special features not specifically related to other project options:
� Positional Tolerance Checking – Selecting this option creates an extra listing section
in the Error Propagation part of the output listing. Some government agencies require
that the positional certainty of points relative to other points in a survey be within
certain a tolerance. For example, the ACSM/ALTA committee in the United States
has set up specifications for this, and they publish tolerances for various classes of
surveys. The allowable tolerance for a connection is the summation of some
published value (such as 0.08 Feet) plus a parts per million (PPM) value calculated
using the horizontal length of the connection.
For any checked connection, a relative ellipse is computed at the specified
confidence region between the two points. The tolerance specification is satisfied
when the semi-major axis ellipse size does not exceed an allowable positional
tolerance calculated for that connection.
When this checking option is turned on, the connections checked by default are all
those containing observations. For small surveys, these connections may be all those
necessary to check. But for larger surveys, you may wish to create other connections
spanning between selected points, not those just between observed points.
See discussion of the “.PTOLERANCE” inline option on page 92. This inline option
is used to generate your own list of connections to be checked.
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