Sokkia Axis 3, Operation Manual

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8 Axis
3™
Chapter 2 Introduction
2.3.1 OmniSTAR signal information
The OmniSTAR satellite correction is a line-of-sight UHF signal
similar to the GPS signal. Various L-Band communications
satellites are used for transmitting the correction data to
OmniSTAR users around the world. The OmniSTAR signal can
be used where beacon signals are not available.
The OmniSTAR service uses geostationary satellites (satellites
that remain stationary in relation to the earth) for
communication. The elevation angle to these satellites is
dependent upon latitude. OmniSTAR provides differential
coverage over most of the land areas of the globe, with the
exception of some areas beyond 60 degrees South Latitude.
However, even within the coverage areas, the user must have a
clear line-of-sight to the satellite.
2.3.2 OmniSTAR Reception and DGPS
The OmniSTAR network functions as a wide-area DGPS
service. The information broadcast by the service is based on a
network of strategic reference stations. The reference stations
communicate GPS correction data to control centers where it is
decoded, checked, and repackaged into a proprietary format for
transmission to a geostationary L-band communications
satellite. This correction data is rebroadcast to the Earth over a
large area where an L-band differential receiver demodulates
the data.
The Axis
3
receiver will process corrections from the wide-area
signal specific to your location. The resulting corrections are
similar to those calculated if a reference station was set up at
your location. This type of solution ensures a consistent level of
accuracy across the entire coverage area.
The OmniSTAR signal is a proprietary wide-area signal (not
RTCM SC-104) with specialized geographically independent
formats. Positioning accuracy will not degrade based on the
distance to a base station. The data is composed of information