4.7.4
GPS
All GeminiG3 radiomodems shipped from the CalAmp factory are fitted with a 12-channel high efficiency GPS
receiver, equipped with WAAS feature for better location precision (<3 meters).
GPS "strings" are collected from embedded GPS receiver in the GeminiG3 mobile radiomodems. The strings
are converted into DCF 2.0 ("Dataradio Compressed Format, version 2.0") reports and provided to both local
and remote delivery services.Programmers who need to decode the compressed information for their applica-
tions may contact CalAmp System Engineering for further information.
Figure 45 - GPS - Status
4.7.4.1
GPS
►
STATUS
Item
Description
Condition
In normal operation, indicates “Differential”. Differential GPS corrects various inaccura-
cies in the GPS system to yield measurements accurate to a couple of meters when the
mobile is moving and even better when stationary.
Other indications are:
Autonomous: GPS values use no additional correction information.
Last known: Indicates GPS data is either old or not enough satellites are present to
achieve a valid location computation.
Invalid: When no GPS signal is present, displays the word “Invalid” and the # of Satel-
lites indicates “0”.
Number SVs
The field “number of satellites” indicates the number of satellite signals being received
and used to calculate position.
UTC (hhmmss)
Universal time - uses a 24-hour clock format.
Position
Global position in Longitude (East-West) and Latitude (North-South) displayed using
information obtained from a GeminiG3 radiomodem decoding a valid GPS input signal.
If no previous position was obtained, display shows (Unknown).
Positions are reported in degrees plus decimal minutes.
E.g.: Longitude of 73 degrees, 39 minutes and 45 seconds West would appear as:
073 39.7500 W
Altitude (meters)
The field “Altitude” indicates height above the WGS-84 (World Geodetic System) refer-
ence ellipsoid in meters.
True Course
Shows the current GPS-generated true course in degrees.
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