Appendix-15
satellite system used in multi-frequency, SBAS or Precise Point Positioning (PPP) mode;
S = Simulator mode;
N = Data not valid.
The mode indicator field should not be a null field.
・GSA – GNSS DOP and active satellites
$--GSA, a, x, xx,xx,xx,xx,xx,xx,xx,xx,xx,xx,xx,xx,x.x,x.x,x.x,h*hh<CR><LF>
1
2 3 4 5 6 7
1：Mode: M = manual, forced to operate in 2D or 3D mode
A = automatic, allowed to automatically switch 2D/3D
2：Mode: 1 = fix not available, 2 = 2D, 3 = 3D
3：ID numbers (see Note 1) of satellites used in solution
4：PDOP
5：HDOP
6：VDOP
7：GNSS System ID (see Note 2)
NOTE 1 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 to 64 are reserved for WAAS satellites. The WAAS system PRN numbers are 120 to 138.
The offset from 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 to 96 are reserved for GLONASS satellites. GLONASS satellites are identified by 64+
satellite slot numbers. The slot numbers are 1 through 24 for the full GLONASS constellation of 24
satellites, thus giving a range of 65 through 88. The numbers 89 through 96 are available if slot numbers
above 24 are allocated to on-orbit spares.
NOTE 2 GNSS System ID identifies the GNSS System ID according to the Table below.
・GSV – GNSS satellites in view
$--GSV, x, x, xx, xx, xx, xxx, xx.............., xx, xx, xxx, xx, h*hh<CR><LF>
1
2 3 4 5 6 7 8 9 10
1：Total number of messages (see Note 1), 1 to 9
2：Message number (see Note 1), 1 to 9
3：Total number of satellites in view
4：Satellite ID number (see Note 3)
5：Elevation, degrees, 90° maximum
6：Azimuth, degrees true, 000 to 359
7：SNR (C/No) 00-99 dB-Hz, null when not tracking
8：Second and third SVs (see Note 2)
9：Fourth SV (see Note 2)
10：Signal ID (see Note 4)
NOTE 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.
NOTE 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 required for unused sets when less than four sets are transmitted.
NOTE 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 to 64 are reserved for WAAS satellites. The WAAS system PRN numbers are 120 to 138.
The offset from 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 to 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
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