My Issues

Drivers Manual

Ashtech GG24 GPS and GLONASS (Position) -12

Description

Driver for Ashtech output sentences, containing Global Positioning System position fix data from Ashtech GG24 Receiver.

The driver will decode position data from $PASHR,POS, $GPRRE and $GLRRE sentences.

Driver Information

Driver Ashtech GG24 GPS and GLONASS (Position)  Interface Type Serial  Driver Class Type Terminated <LF> 
UTC Driver (question)  No Input / Output Input (User Interface)  Executable

DrvAshtechGG24.exe

Related Systems
Related Pages  



Interfacing Notes

The Ashtech GG24 receiver has got three male 9 pin connectors for serial input/output: port A, B and C. A typical setup could be to use port A to output the position, port B to output the PPS time tag and to use port C to receive differential corrections from a shore station (via a Satel box). Some specific commands, using the Ashtech "$PASHS" format, have to be sent to the GG24 receiver to enable these user-definable I/O options.

Communications with the Ashtech GG24 receiver require handshaking, so the usual wiring of only the pins 2, 3 and 5 (RXD, TXD and Signal Ground) is not sufficient. One must use a specific serial interface cable or wire an interface cable according to the standard RS-232C (DTE Wiring) protocol, see Wiring Diagram 1. See Wiring Diagram 2 for the wiring from receiver port C to the Satel box, which has a 15 pins connector.

The PPS pulse is output as a TTL pulse on pin 9 of port A. The Ashtech manual refers to this pulse as the TTT event marker. The signal must be converted by the QPS PPS/fix box, via a coax cable, as follows. The BNC connector goes to "Fix In" of the PPS/fix box, the other end of the coax cable must be connected to pin 9 (PPS pulse) and pin 5 (signal ground) of GG24 port A. In order to receive the time tag message, one must split the same PPS signal from port A and feed it back into port B of the Ashtech GG24 receiver, i.e.pin 9 port A (PPS pulse out) to pin 9 port B (Event pulse in) and pin 5 port A to pin 5 port B (Signal Ground).

Refer to the sections "Ashtech PPS" and "Ashtech ADU2" for more detailed information on system setup.

GG24

COM

COM

DB-9

DB-9

DB-25

1 + 6

----

4

20

2

----

3

2

3

----

2

3

4

----

1 + 6

6

5

----

5

7

6 + 1

----

4

20

7

----

8

5

8

----

7

4

9

----

X

X

Wiring Diagram 1

GG24

SATEL

DB-9

DB-15

1

----

X

2

----

9

3

----

11

4

----

15

5

----

8

6

----

7

7

----

6

8

----

13

9

----

X

1 + 14

3 + 4

Wiring Diagram 2

Online

First time online, restore the "Ashtech GG24" driver window on the Windows taskbar and set the validation options, by selecting menu "Options - Validation Settings..." or pressing the left button "Change Settings".

The user can define allowable position mode, position error limits, minimum number of satellites and DOP limits. Another user-definable option is the logging of (discarded or all) position data to an ASCII file.

Use a "Positioning System Display" to see the satellites that were used to compute the GPS position and the PDOP and RMS values. Use an "Alert Display" to setup a "Position RMS outside limit" raw data alert.

Use an "Observation Physics Display" to see the three components of the RMS value as quality indicator, or a "Position System Display" where they are the SD-values for the latitude, longitude and height observation.