Reference Information
LD900 Installation and Oper ations M anual
69
6.4.5 GSA Sentence
The NMEA GSA sentence contains the GNSS receiver operating mode, active satellites used in the navigation
solution, and DOP values.
GSA Sentence Structure & Example
$GNGSA, a, 1, cc, cc, cc, cc, cc, cc, cc, cc, cc, cc, cc, cc, d.d, e.e, f .f *hh
$GNGSA, a, b, 02, 12, 15, 20, 21, 24, 25, 29, 32, , , , 1.7, 0.9, 1.5 *58
GSA Sentence Defined
Field
Content
GSA
GNSS DOP and active satellites
a
Mode (M = Manual mode, forced to operate in 2D or 3D mode,
A = Automatic mode, allowed to automatically switch 2D/3D)
b
Fix (1 = Not available, 2 = 2D, 3 = 3D)
cc
PRN ID numbers of satellites used in solution a total of 12 fields
GPS = 1 to 32
GLONASS = 65 to 96
As shown in the above example, if less than 12 satellites for one constellation are used null
values will be output in the string.
d.d
PDOP
e.e
HDOP
f.f
VDOP
hh
Checksum
6.4.6 GSV Sentence
The NMEA GSV sentence provides information relating to the number of satellites (SV) in view, satellite ID
numbers, elevation, azimuth, and SNR value in one sentence.
GSV Sentence Structure & Example
$GPGSV, a, b, cc, dd, ee, f ff, gg, dd, ee, f ff, gg, dd, ee, f ff, gg, dd, ee, f ff, gg, *hh,
$GPGSV, 4, 1, 13, 02, 10, 043, 41, 05, 05, 103, 38, 10, 04, 238, 42, 12, 13, 030, 44, *7E,
(Satellite 1)
(Satellite 2)
(Satellite 3)
(Satellite 4)
GSV Sentence Defined
Field
Content
GSV
GNSS satellites in view
a
Total number of sentences (1-9)
b
Sentence number (1-9)
cc
Total number of satellites in view, within the talker ID constellation
dd
Satellite ID number
GPS = 1 to 32
GLONASS = 65 to 96
ee
Elevation, degrees (90° maximum)
fff
Azimuth, degrees true, 000 to 359
gg
SNR (C/No) 00-99 dB-Hz, null when not tracking
hh
Checksum
NOTE
Fields dd, ee, fff and gg will be repeated 4 times per sentence, where all satellite info is already output null
values will be output.
