Hemisphere GPS V104s, User Manual

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Chapter 3: Operation
GPS Overview
For your convenience, both the GPS and SBAS (WAAS, MSAS, GAGAN and
EGNOS) operation of the V104s features automatic operational algorithms.
When powered for the first time, the V104s 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
V104s’s internal GPS receiver.
Note:
Differential source and status have no impact on heading, pitch, or
roll. They only have an impact on position and heave.
Automatic Tracking
The V104s’s internal GPS receiver automatically searches for GPS satellites,
acquires the signals, and manages the navigation information required for
position and tracking.
Receiver Performance
The V104s works by finding four or more GPS satellites in the visible sky. It
uses information from the satellites to compute a position within 3 m. Since
there is some error in the GPS data calculations, the V104s also tracks a
differential correction. The V104s 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
• Position and heading calculation