GeoGenius: GPS post-processing
GeoGenius from Terrasat is a user-friendly GPS post-processing application running under Windows. It includes a macro language to automate most of its functions. The macro language is an extension of TCL which is well documented.
The Autoprocess macro detailed in this document assumes the following:
1) an EMEWS database is available on the system, this database is used to store parameters, processing results and links to observation (GeoGenius format) and ephemeris files (RINEX format)
2) each GPS receiver is assigned its own directory where raw files are deposited. These raw files must be in a format supported by GeoGenius (Ashtech BES, Trimble, RINEX, … ) and can be generated by the following acquisition software:
- ALDO from IIV, retrieving data files via modem connections
- GG-Base from Terrasat, controls up to 9 receivers
- GBSS from Ashtech
- and any other manufacturer software that can regularly create files on the disk in a format supported by GeoGenius
3) there is one and only one reference station on the network, its position is fixed and position of other stations are computed related to this reference and stored in the database
4) the directory of the reference station also contains ephemeris files, this file has the same name than the observation file but with extension « .YYn »
5) each GPS stations has the following channels defined in the database: GPS_OBS, COOR_N, COOR_E, COOR_U, Nb_Sats, RMS. The reference station has an additional channel GPS_EPHEMERIS.
6) an archiving directory is defined by the environment variable RINEXOUT
The autoprocess macro will scan the selected directories for new raw files. If a new file is found it will be loaded into GeoGenius which will convert it into the GeoGenius observation format (.OBS). This OBS file will be moved to an archive directory and a link to this new location will be inserted in the EMEWS database. If the observation file was created by the reference station, the corresponding ephemeris file will be also archived and recorded in the database.
Then the database will be queried to find if a matching file is available for processing. If the file belongs to the reference all other stations will be queried, if the file is not from the reference then only the reference will be queried.
If a match is found a GeoGenius project is created for processing. These projects include only two observations files: one from the reference and the other from a « rover » station. No network adjustment is performed.
The position of the « rover » is computed and the lat, long, elev are stored in the database. The NB_SATs and RMS parameters are also stored for quality analysis.
This version will loop forever, pausing 1 minute between each scan.
1. download tclodbc.zip from http://megamail.solagem.fi/~rnurmi/tclodbc.html
2. copy the file tcl8.0\tclodbc.dll into the GeoGenius installation directory
3. copy autoprocess.m into the GeoGenius installation directory
4. Make sure that an EMEWS database is available and that an Access or Sybase ODBC driver is configured.
5. Open the EMEWS database in MS-Access and make sure that:
– each of your GPS station have the channels GPS_OBS, COOR_N, COOR_E, COOR_U, NB_SATs, RMS defined.
– that one and only one station has the « GPSnet_ref » field of its RINEX channel set to Yes. This is the reference.
– that this reference as an additional channel called GPS_EPHEMERIS
– that the field « incoming_directory » of each GPS_OBS channel is defined and that it exists on the disk. This is where acquisition applications will deposit new files.
– that the archiving directory exists and is defined by the environment variable RINEXOUT. On Win95/98, environment variable are defined in the autoexec.bat with SET varname=value, example: SET RINEXOUT=E:\GPS. On WinNT use the control panel, system.
– that the reference is linked to a valid location record, lat and lon are in degree (N, E positive or S, W negative), elev is in meters
the sample MS-Access database already includes two stations: AAA and CCC
6. Check in the Control Panel, Regional Settings that your time displays in 24h format and not in 12h.
Manually running the macro
1) Start GeoGenius
2) In the menu File, select Run, Macro File and select the file autoprocess.m
Automatically running the macro when the computer boots
create a shortcut to GeoGenius and edit the command line so that it looks like:
gg20.exe -m autoprocess.m
Windows95 users: move this link to the Startup or Démarrage folder
WindowsNT users: this command line must be installed as a service. The installation procedure is a bit complex, read the following document from Campbell and use the NT utilities provided.
Important: when running as a service on NT, environment variable are not visible. So the script must be customized with the actual values, ex: set archive_dir E:\\GPS