Leica Geosystems GPS Basics - Manual (Page 39)

39
GPS Basics -1.0.0en Surveying with GPS
5.1 GPS Measuring Techniques
There are several measuring techniques
that can be used by most GPS Survey
Receivers. The surveyor should choose
the appropriate technique for the appli-
cation.
Static - Used for long lines, geodetic
networks, tectonic plate studies etc.
Offers high accuracy over long distances
but is comparatively slow.
Rapid Static - Used for establishing
local control networks, Network densifi-
cation etc. Offers high accuracy on
baselines up to about 20km and is
much faster than the Static technique.
Kinematic - Used for detail surveys and
measuring many points in quick succes-
sion. Very efficient way of measuring
many points that are close together.
However, if there are obstructions to the
sky such as bridges, trees, tall buildings
etc., and less than 4 satellites are
tracked, the equipment must be
reinitialized which can take 5-10 min-
utes.
A processing technique known as On-
the-Fly (OTF) has gone a long way to
minimise this restriction.
RTK - Real Time Kinematic uses a radio
data link to transmit satellite data from
the Reference to the Rover. This enables
coordinates to be calculated and
displayed in real time, as the survey is
being carried out. Used for similar
applications as Kinematic. A very effec-
tive way for measuring detail as results
are presented as work is carried out.
This technique is however reliant upon a
radio link, which is subject to interfer-
ence from other radio sources and also
line of sight blockage.