SECTION 2
RECEIVER OPERATION
Upon power up, after initial self-test has completed, the HI-203E will begin
satellite acquisition and tracking process. Under normal open-sky condition,
position-fix can be achieved within approximately 45 seconds (within 15
seconds if valid ephemeris data is already collected from recent use). After
receiver position has been calculated, valid position, velocity and time
information are transmitted through the on board serial interface.
The receiver uses the latest stored position, satellite data, and current
RTC time to achieve rapid GPS signal acquisition and fast TTFF. If the
receiver is transported over a large distance across the globe, cold-start
automatic-locate sequence is invoked. The first position fix may take up
to five minutes searching the sky for the GPS signal. The acquisition
performance can be improved significantly if the host initializes the
receiver with a rough estimate of time and user position.
As soon as GPS signal is acquired and tracked, the HI-203E will
transmit valid navigation information through its serial interface. The
navigation data contains following information:
• Receiver position in latitude, longitude, and altitude
• Receiver velocity
• Time
• DOP error-magnification factor
• GPS signal tracking status
The HI-203E will perform 3D navigation when four or more satellites are
tracked. When three or fewer satellites are tracked, altitude-hold is enabled
using the last computed altitude and 2D navigation mode is entered.
With signal blockage or rising and setting of the satellites, where a
change in satellite constellation used for position fix occurred, large
position error may result. The HI-203E incorporates a proprietary
algorithm to compensate the effect of satellite constellation change, and
maintains an accurate smooth estimate of the receiver position, velocity,
and heading.
6
Summary of Contents for HI-203E
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