Hemisphere GPS V102 G, Руководство пользователя, Страница: 33 / 60

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Chapter 3: Operation
GPS Overview
For your convenience, both the GPS and SBAS operation of the V102
features automatic operational algorithms. When powered for the first time,
the V102 performs a "cold start," which involves acquiring the available GPS
satellites in view and the SBAS differential service.
If SBAS is not available in your area, an external source of RTCM SC-104
differential corrections may be used. If you use an external source of
correction data, it must support an eight data bit, no parity, one stop bit
configuration (8-N-1).
GPS Operation
The GPS receiver is always operating, regardless of the DGPS mode of
operation. The following sections describe the general operation of the
V102’s internal GPS receiver.
Note: Differential source and status have no impact on heading, pitch, or
roll. They only have an impact on positioning and heave.
Automatic Tracking
The V102’s internal GPS receiver automatically searches for GPS satellites,
acquires the signals, and manages the navigation information required for
positioning and tracking.
Receiver Performance
The V102 works by finding four or more GPS satellites in the visible sky. It
uses information from the satellites to compute a position within 2.5 m.
Since there is some error in the GPS data calculations, the V102 also tracks a
differential correction. The V102 uses these corrections to improve its
position accuracy to better than 1.0 m.
There are two main aspects of GPS receiver performance:
• Satellite acquisition
• Positioning and heading calculation