of characters from the beginning of the sentence.
The last data field is not followed by a comma delimiter.
When a checksum is used, the last data field is followed
by an asterisk “*”, indicating that the checksum follows.
The checksum is the absolute value calculated by
exclusive -OR’ing the 8 data bits (no start bits or stop
bits) of each character in the sentence between, but
excluding “$” and “*”. The hexadecimal value of the most
significant and least significant 4 bits of the result are
converted to two ASCII characters (0- 9, A- F) for trans-
mission. The most significant character is transmitted
first.
Example:
$GPXTE,A,A,3.42,L,N*hh<CR><LF>
Field #: 1 2 3 4 5 6 7 8 9
Sentence terminator
Optional checksum (HEX)
In Ver. 1.5 & 2.0, required in Ver 2.1
Checksum delimiter
Units of measure, N=nautical miles
Direction to steer, L=Left, R=Right
Magnitude of error (nautical miles)
Not used, Always = A
Status: A=Data valid, V=Data invalid
Start of Sentence delimiter
Address: GP = Talker identifier: GPS
XTE= Sentence formatter: Cross-Track Error
NMEA Output Sentences
All sentences have the identifier “GP” for Global
Positioning Systems. All position data are in the user
selected (displayed) datum except for GGA where the da-
tum can be manually set to WGS84, independent of the
selected (displayed) datum.
RMB is transmitted only if an active route is pres-
ent. Please refer to the Route section of the Operator’s
Manual for details on setting up an active route.
APA, APB and XTE are transmitted only if an active
route is present and the Autopilot Alarm in each of these
NMEA sentence setup screens is Enabled and this feature
is not in an alarm condition.
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