GSA - GPS DOP and Active Satellites

GSA - GPS DOP and Active Satellites

This command enables the GPGSA GPS DOP and active satellites message and determines the rate at which the information is transmitted. The periodic rate field (yyyy) instructs the receiver either to output this message once (polled), or to output this message at the indicated update rate (continuously). Once the receiver is set to continuous output, the continuous flow can be stopped by sending a one-time (polled) output request. The receiver will output the response one final time, and then terminate any further message outputs. The value of the periodic rate is retained through a power cycle only if battery back-up power is applied.

If the receiver is not computing a position fix (mode field (b) is one), then the xDOP fields (p.p, q.q, r.r) will be nulled. If the receiver is computing a 2-D position fix (mode field (b) is two), then the PDOP field (p.p) and the VDOP field (r.r) will be nulled. Only satellite IDs used in the solution are output; the remaining satellite ID fields will be nulled.

Input Command

• Set response message rate:

  $PMOTG,GSA,yyyyCC

  yyyy	update rate	0 .. 9999 seconds
  CC	optional checksum

Response Message

• Response to above command at selected rate:

  $GPGSA,a,b,cc,dd,ee,ff,gg,hh,ii,jj,kk,mm,nn,oo,p.p,q.q,r.r*CC

  a	sat acquisition mode	M = manual
  		(forced to operate in 2D or 3D mode)
  		A = automatic (auto switch 2D/3D)
  b	positioning mode	1 = fix not available
  		2 = 2D
  		3 = 3D
  cc, dd, ee, ff, gg, hh,ii, jj, kk, mm, nn, oo	sat IDs used in solution	(null for unused fields)
  p.p	PDOP	1.0 .. 9.9
  q.q	HDOP	1.0 .. 9.9
  r.r	VDOP	1.0 .. 9.9
  CC	checksum