User's Manual Part 1

Positioning Modes of Operation Chapter 5
OEMV Family Installation and Operation User Manual Rev 5B 85
5.4 L-Band Positioning
The transmission of OmniSTAR or CDGPS corrections are from geostationary satellites. The L-Band
frequency of geostationary satellites is sufficiently close to that of GPS that a common, single
antenna, such as the NovAtel GPS-702L, may be used.
Both systems are portable and capable of sub-meter accuracy over their coverage areas. See also
Figure 29, L-Band Concept on Page 89.
The OmniSTAR system is designed for coverage of most of the world’s land areas. A subscription
charge by geographic area is required. The CDGPS system is a free Canada-wide DGPS service that is
accessible coast-to-coast, throughout most of the continental United States, and into the Arctic.
5.4.1 Coverage
The two systems provide different coverage:
• OmniSTAR - Most of the World’s Land Areas
• CDGPS - Canada/America-Wide
OmniSTAR Geographic Areas
In most world areas, a single satellite is used by OmniSTAR to provide coverage over an entire
continent - or at least very large geographic areas. In North America, a single satellite is used, but it
needs three separate beams to cover the continent. The three beams are arranged to cover the East,
Central, and Western portions of North America. The same data is broadcast over all three beams, but
the user system must select the proper beam frequency. The beams have overlaps of several hundred
miles, so the point where the frequency must be changed is not critical.
The North American OmniSTAR Network currently consists of ten permanent base stations in the
Continental U.S., plus one in Mexico. These eleven stations track all GPS satellites above 5 degrees
elevation and compute corrections every 600 milliseconds. The corrections are sent to the OmniSTAR
Network Control Center (NCC) in Houston via wire networks. At the NCC these messages are
checked, compressed, and formed into packets for transmission up to the OmniSTAR satellite
transponder. This occurs every few seconds. A packet contains the latest corrections from each of the
North American base stations.
All of the eastern Canadian Provinces, the Caribbean Islands, Central America (south of Mexico), and
South America is covered by a single satellite (AM-Sat). A single subscription is available for all the
areas covered by this satellite.
OmniSTAR currently has several high-powered satellites in use around the world. They provide
coverage for most of the world's land areas. Subscriptions are sold by geographic area. Any Regional
OmniSTAR service center can sell and activate subscriptions for any area. They may be arranged prior
to travelling to a new area, or after arrival. Contact OmniSTAR at www.omnistar.com
for details.