Re: basic information about how GPS is used for Land Surveys

bob bookouri (bookouri@xxxxxxxxx) wrote:
with editing...
: Id like to learn more about how GPS is used for land surveying. Can
: anyone point me toward any sources of information? Ive looked around
: at a lot of "surveying" type sites, but I find more info about the
: equipment being used than "how" GPS is actually used to produce a
: survey.

Observations are taken simultaneously from first-order survey
monuments and unknown ground points.
The coords obtained by GPS for the known monuments are then
compared to determine if the measurements are acceptable.
If they are, then the distances between any two points
are calculated using the GPS coordinates.
At this point, the GPS coords are discarded, and the
distances between points are retained.
The distances are then fed to a trilateration network
adjusting program and adjusted by least-squares methods
on (massively) over-determined networks, as they have
been for 100+ years.

Coordinates and azimuths (bearings to you) obtained by GPS
are not accurate enough for survey work, but the distances
obtained from the coords can be used in survey calculations.

But the act of discarding the coords is integrated into the
least-square eqns. so you could not point to a place in the
calculations and say the coords are discarded at this point.

Hope that simplifies it a bit.

Regards. RAF (survey engineer/geomatics engineer)
.

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