Celestron NexStar GPS Betriebsanweisung PDF herunterladen (Seite 37)

Satellite info 29

NexStar AUX Command Set Issue 1.0

Satellite info

The GPS_GET_SAT_INFO command returns two bytes:

• the number of satellites currently visible to the GPS module

• the number of satellites being tracked

The count of visible satellites seems to take a long time to become valid while the

count of tracked satellites is updated very frequently. By blocking the GPS antenna

(located in the fork arm with the handle) with your hand, you can watch these

values change in response to the changing signal.

Receiver status

The GPS_GET_RCVR_STATUS command returns two bytes with information about

the status of the GPS receiver. This data is in a bit-mapped format as follows:

Bit 15-13: 111 = 3D Fix

110 = 2D Fix

101 = Propagate Mode

100 = Position Hold

011 = Acquiring Satellites

010 = Bad Geometry

001 = Reserved

000 = Reserved

Bit 12-11: Reserved

Bit 10: Narrow track mode (timing only)

Bit 9: Fast Acquisition Position

Bit 8: Filter Reset To Raw GPS Solution

Bit 7: Cold Start (no almanac out of date or

have almanac nut time or position unknown)

Bit 6 Differential Fix

Bit 5: Position Lock

Bit 4: Autosurvey Mode

Bit 3: Insufficient Visible Satellites

Bit 2-1: Antenna Sense 00 = OK

01 = OC

10 = UC

11 = NV

Bit 0: Code Location 0 = EXTERNAL

1 = INTERNAL

This information can be found in chapter 5 of Motorola’s GPS user’s guide at:

http://www.motorola.com/ies/GPS/products/positioningmodules.html

When the GPS module is searching for satellites, bits 15-13 are set to

Acquiring

Satellites

. Once there is enough data for a link, these bits change to 2D Fix. If

there is enough signal and satellites, this values changes to

3D Fix.

1 2 ... 32 33 34 35 36 37 38 39 40 41 42 ... 45 46

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