CSI Wireless DGPS MAX, Reference Manual

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DGPS MAX Reference Manual
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The world beacon networks continue to expand. For more current
coverage, consult the CSI Wireless Web site at
www.csi-wireless.com .
1.6 DGPS Service Comparison
As the DGPS MAX offers the use multiple differential services, questions
have been raised in regards to which correction source to use when more
than one is available. Ultimately, this is a personal choice, however, this
section provides some information that may help you choose which
service is most appropriate for you. In the end, it may be best to try each,
if possible, to determine which is most appropriate.
There are four scenarios that may occur for multiple DGPS service
availability:
n
WAAS, OmniSTAR, and beacon are each available
n
WAAS and OmniSTAR are available
n
WAAS and beacon are available
n
OmniSTAR and beacon are available
Beacon signals are not affected by a line of sight. In situations where there
are tall obstacles that may block the line of sight DGPS signal (both WAAS
and OmniSTAR), such as buildings or trees, a beacon signal may be more
desirable. However, the value of our new COAST™ technology, discussed
in Section 1.8, is that outages of the DGPS signal are less of an influence on
reception. This improves the robustness of using a line of sight signal in
areas of potential blockage. If robustness to signal acquisition due to line of
sight is considered a significant issue, beacon DGPS should be considered
in replace of WAAS or OmniSTAR services.
All three services use base stations to calculate GPS correction data.
Beacons use a single, local base station for corrections, while WAAS and
OmniSTAR use a wide area network of stations. If there is a significant
distance to the closest beacon (greater than a 200 - 300 hundred miles),
this will have an effect on positioning accuracy due to differing