DM-0210
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 $GLRRE sentences.
Driver Information
| Driver | Ashtech GG24 GPS and GLONASS (Position) | Interface Type | Serial | Driver Class Type | Terminated <LF> |
|---|---|---|---|---|---|
UTC Driver  | No | Input / Output | Input (User Interface) | Executable | DrvAshtechGG24.exe |
| Related Systems | |||||
| Related Pages | |||||
Interfacing Notes
The Ashtech GG24 receiver has got three male 9 pin connectors for serial input/output: port A, B and C. A typical setup could be to use port A to output the position, port B to output the PPS time tag and to use port C to receive differential corrections from a shore station (via a Satel box). Some specific commands, using the Ashtech "$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.