Spectra Precision Survey Pro v4.5 Ranger User Manual - Manual (Page 198)

User’s Manual – GPS Mode
188
¾ A description of using Ground Coordinates on a reference
mapping plane.
¾ A description of geoid modeling and how to use geoid models
for vertical transformations.
RTK and Post Processing
Using GPS for precise survey measurements requires data from two
receivers to be collected simultaneously. There are two common
methods for calculating positions with this data: Real Time
Kinematic (RTK) and post processing.
In an RTK survey, at least one receiver acts as a base station,
collecting GPS measurements and broadcasting the raw data over a
modem link such as a radio, cell phone, or an Internet IP connection.
The other receiver acts as a rover, receiving the base data and
combining it with its own measurements for a real time solution of
position at the rover.
The rover receiver can get the base data from a single base station
setup in the field, or from a computer server delivering the base data
over the Internet. Base data delivered over the Internet can use one
of two methods: Single base, or Virtual Reference Station (VRS).
Using data from a single base over the Internet is essentially the
same as using a base station setup in the field. In this case the rover
receives data from a single base station and calculates its RTK
position where the expected precision is a function of the distance
between the rover and the base. Using data from a VRS involves the
network software calculating corrections from multiple base stations
in the network. In this case, the rover receives data corrected for
systematic errors and can calculate its RTK position with a precision
similar to short baselines, even though the real distance to the base
stations may be quite long.
In a post processing survey, two or more receivers log raw GPS
measurements simultaneously to a file in the field. Then, the data is
downloaded onto a computer where the differential solution is
calculated (post processed) after the field data collection is completed.
Survey Pro can control GPS receivers for RTK, RTK simultaneous
with post processing, and post processing only data collection.