C-Nav 2050, User Manual

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2050 User Guide
Data Field
Data fields contain data associated with the Sentence Identifier code. The format of
the Data Field is determined by the Sentence Identifier code format value which for
the C-Nav GPS Receiver and the CnC D.U. are as follows:-
[Address Field]
[Data Field Information]
Talker
ID
Sentence
ID NMEA Sentence Description
GP ALM Global Positioning System Almanac Data
GP GGA
Global Positioning System Fix Data
GP GLL GPS Latitude and Longitude Data
GP GSA GPS Mode, Satellites used for navigation, and DOP Data
GP GST GPS Satellites Position Error Statistics (RAIM compliance)
GP GSV GPS Satellites Position and L1 signal tracking Data
GP RMC GPS Recommended Minimum Specific Data
GP VTG GPS Velocity, Track made good and Ground speed Data
GP ZDA GPS UTC Date & Time Data
Table D. 1 C-Nav[2050] NMEA Sentences
The NMEA sentence data fields contain one or more fields, each separated, or
proceeded, by the comma character (,).
The checksum field is preceded by the asterisk character (*), and is the 8-bit
exclusive OR (no start or stop bits) of all characters in the sentence, including the
comma character (,) delimiters, between (but not including) the dollar character ($)
and asterisk character (*) delimiters.
The hexadecimal values, of the result, are converted to two ASCII characters (0-9, A-
F) for transmission. The most significant character is transmitted first.
Null fields are included in the format for the NMEA 0183 sentence format. These are
used when no data is available for a particular field in the sentence format. Null fields
are empty and defined to be immediately followed by the comma delimiter for the
next field in the sentence string format.
The inclusion of Null fields in the sentence format allows the fixed number of data
fields to be maintained, and that the sentence field delimiters (the commas) allow the
NMEA sentence interpretation routines and interfaces to properly function. If a Null
field is encountered, it is assumed that no data is available for the defined sentence
field.
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