Manual Title:
LD7 Operations Manual
Ref.:
AB-V-MA-00555
Rev No:
A9
Page 49
NMEA GSV Sentence
GSV sentence defined:
GNSS Satellites In View
Number of satellites (SV) in view, satellite ID numbers, elevation, azimuth, and SNR value. Four
satellites maximum per transmission. Total number of sentences being transmitted and the number
of the sentence being transmitted are indicated in the first two fields.
If multiple GPS, GLONASS, etc. satellites are in view, use separate GSV sentences with talker ID
GP to show the GPS satellites in view and talker GL to show the GLONASS satellites in view, etc.
The GN identifier shall not be used with this sentence.
Notes:
1) Satellite information may require the transmission of multiple sentences all containing identical
field formats when sending a complete message. The first field specifies the total number of
sentences, minimum value 1.
The second field identifies the order of this sentence (sentence number), minimum value 1. For
efficiency it is recommended that null fields be used in the additional sentences when the data is
unchanged from the first sentence.
2) A variable number of "Satellite ID-Elevation-Azimuth-SNR" sets are allowed up to a maximum of
four sets per sentence. Null fields are not required for unused sets when less than four sets are
transmitted.
3) Satellite ID numbers. To avoid possible confusion caused by repetition of satellite ID numbers
when using multiple satellite systems, the following convention has been adopted:
a) GPS satellites are identified by their PRN numbers, which range from 1 to 32.
b) The numbers 33-64 are reserved for WAAS satellites. The WAAS system PRN numbers are
120-138. The offset from NMEA WAAS SV ID to WAAS PRN number is 87. A WAAS PRN
number of 120 minus 87 yields the SV ID of 33. The addition of 87 to the SV ID yields the
WAAS PRN number.
c) The numbers 65-96 are reserved for GLONASS satellites. GLONASS satellites are identified
by 64+satellite slot number. The slot numbers are 1 through 24 for the full GLONASS
constellation of 24 satellites, this gives a range of 65 through 88. The numbers 89 through 96
are available if slot numbers above 24 are allocated to on-orbit spares.
