Oxford Technical Solutions
8
How do base stations work?
A base station significantly increases the position accuracy of mobile GNSS receivers by
sending them corrections. The base station does this by independently identifying the errors
affecting the signal from each GNSS satellite it can see. Information about those errors is then
broadcast via radio modem or something similar. Other GNSS receivers in the area—which
are also connected to similar radio modems—receive the correction information and take it
into account when calculating their own position measurements. Removing the errors results
in more accurate position estimates.
A base station identifies the errors affecting GNSS signals in one of two ways. If the base
station is placed at a precisely surveyed location, it calculates a GNSS position measurement
in the normal way, then compares that calculated position to the known location. If the
position measurements match exactly, no correction is required. If there is a difference
however, the base station calculates the length of time each satellite signal would need to be
delayed by, in order to cause the difference between the surveyed location and the GNSS
measurement being produced.
Introduction
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The GPS-Base is a highly-portable GPS base station that transmits differential corrections to
one or more differential enabled GNSS receivers via radio modem. The position accuracy of
differential and RTK GNSS receivers is improved when using the GPS-Base. The GPS-Base
is available with several different radio options. Different radios are required for license free
operation in different countries.
Four models of the GPS-Base exist, as listed in Table 1. All models are identical in their
operation but are able to track different satellite signals.
Table 1.
GPS-Base models
Model
Measurement/Accuracy potential
a
a. Note: The maximum positioning accuracy is determined by the GNSS hardware in the mobile
receiver.
GPS-Base-2
L1/L2 GPS corrections suitable for positioning down to 1 cm accuracy
GPS-Base-2G
L1/L2 GPS and L1/L2 GLONASS corrections suitable for positioning down to
1 cm accuracy
