Operation; Gps Overview - Simrad HS60 User Manual

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Operation

GPS overview

For your convenience, both the GPS and SBAS (WAAS, MSAS,
GAGAN and EGNOS) operation of the HS60 features automatic
operational algorithms. When powered for the first time, the HS60
performs a "cold start, " which involves acquiring the available GPS
satellites in view and the SBAS differential service.
GPS Operation
The GPS receiver is always operating, regardless of the DGPS mode
of operation. The following sections describe the general operation
of the HS60's internal GPS receiver.
¼ 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 HS60's internal GPS receiver automatically searches for GPS sat-
ellites, acquires the signals, and manages the navigation information
required for position and tracking.
Receiver performance
The HS60 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 HS60 also tracks a differential correction. The HS60 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
When the HS60 is properly positioned, the satellites transmit coded
information to the antennas on a specific frequency. This allows
the receiver to calculate a range to each satellite from both anten-
nas. GPS is essentially a timing system. The ranges are calculated by
timing how long it takes for the signal to reach the GPS antenna.
The GPS receiver uses a complex algorithm incorporating satellite
locations and ranges to each satellite to calculate the geographic
location and heading. Reception of any four or more GPS signals
allows the receiver to compute three-dimensional coordinates and
a valid heading.
Operation | HS60 GPS Compass User Guide