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Operation
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GPS/GLONASS Receiver User Manual Rev 1
4.6.4 NMEA FORMAT DATA LOGS
4.6.4.1 General
The NMEA log structures follow format standards as adopted by the National Marine Electronics Association
(NMEA). The reference document used is "Standard For Interfacing Marine Electronic Devices NMEA 0183
Version 2.20". For further information, refer to the MiLLennium Command Descriptions Manual, Appendix F,
Standards and References. The following table contains excerpts from the NMEA Standard which defines the
variables for the NMEA logs. 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:
degrees|minutes.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:
degrees|minutes.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:
hours|minutes|seconds.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 numbers
x.x
Variable length integer or floating numeric field. Optional leading and trailing
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 field
hh___
Fixed length HEX numbers only, MSB on the left
Information Fields
Variable text
c--c
Variable length valid character field.
Fixed alpha field
aa___
Fixed length field of uppercase or lowercase alpha characters
Fixed number field
xx___
Fixed length field of numeric characters
Fixed text field
cc___
Fixed length field of valid characters
NOTES:
1.
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.
