Veripos LD6 Operation Manual page 84

Procedure Title: LD6 Operations Manual (B Variant)
File Ref.: AB-V-MA-00589
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.
Rev No: A4 Page 84