Novatel OM-20000077 user manual Nmea Format Data Messages, Message Formats Chapter

Message Formats Chapter 5

Type 9 messages contain the following information for a group of three satellites in view at the base station:

•Scale factor

•User Differential Range Error

•Satellite ID

•Pseudorange correction

•Range-rate correction

•Issue of Data (IOD)

5.2NMEA Format Data Messages

The NMEA log structures follow format standards as adopted by the National Marine Electronics Association. The reference document used is "Standard For Interfacing Marine Electronic Devices NMEA 0183 Version 2.00". For further information, see Appendix D, Standards/References on Page 62. The following table contains excerpts from Table 6 of the NMEA Standard which defines the variables for the NMEA messages. The actual format for each parameter is indicated after its description.

Field Type Symbol

Definition

Special Format Fields

Status		A	Single character field:
			A = Yes, Data Valid, Warning Flag Clear
			V = No, Data Invalid, Warning Flag Set
Latitude		llll.ll	Fixed/Variable length field:
			degreesminutes.decimal - 2 fixed digits of degrees, 2 fixed digits of minutes and
			a variable number of digits for decimal-fraction of minutes. Leading zeros always
			included for degrees and minutes to maintain fixed length. The decimal point and
			associated decimal-fraction are optional if full resolution is not required.
Longitude		yyyyy.yy	Fixed/Variable length field:
			degreesminutes.decimal - 3 fixed digits of degrees, 2 fixed digits of minutes and
			a variable number of digits for decimal-fraction of minutes. Leading zeros always
			included for degrees and minutes to maintain fixed length. The decimal point and
			associated decimal-fraction are optional if full resolution is not required
Time		hhmmss.ss	Fixed/Variable length field:
			hoursminutesseconds.decimal - 2 fixed digits of hours, 2 fixed digits of minutes,
			2 fixed digits of seconds and variable number of digits for decimal-fraction of
			seconds. Leading zeros always included for hours, minutes and seconds to
			maintain fixed length. The decimal point and associated decimal-fraction are
			optional if full resolution is not required.
Defined field			Some fields are specified to contain pre-defined constants, most often alpha
			characters. Such a field is indicated in this standard by the presence of one or
			more valid characters. Excluded from the list of allowable characters are the
			following which are used to indicate field types within this standard:
			"A", "a", "c", "hh", "hhmmss.ss", "llll.ll", "x", "yyyyy.yy"
Numeric Value Fields
Variable		x.x	Variable length integer or floating numeric field. Optional leading and trailing
numbers			zeros. The decimal point and associated decimal-fraction are optional if full
			resolution is not required (example: 73.10 = 73.1 = 073.1 = 73)
Fixed HEX		hh___	Fixed length HEX numbers only, MSB on the left
Information Fields
Variable text		c--c	Variable length valid character field.
Fixed alpha		aa___	Fixed length field of uppercase or lowercase alpha characters
Fixed number		xx___	Fixed length field of numeric characters
Fixed text		cc___	Fixed length field of valid characters
1.			NOTES:
	Spaces may only be used in variable text fields.
2.	A negative sign "-" (HEX 2D) is the first character in a Field if the value is negative. The sign is omitted if value is positive.
3.	All data fields are delimited by a comma (,).
4.	Null fields are indicated by no data between two commas (,,). Null fields indicate invalid or no data available.
5.	The NMEA Standard requires that message lengths be limited to 82 characters.

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