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A comparative study of results from GPS data processing software
- Bernese Software Version 4.2
Bernese software has been designed by the University of Bern to meet high accuracy required for scientific purposes. The following are the steps involved in the Bernese processing
- Campaign module: The first task is to setup the campaign and create the basic directories required for the processing.
- Transfer module: Transfer of DAT to RINEX (TRINEXO) and RINEX to Bernese (RXOBV3)
- Orbital module: Two programs are run PRETAB and ORBGEN to get clock file and standard files. To get more precise results IGS precise file has to be downloaded and used.
- Processing module: In this module five programs are run in order to get the final solution.
| CODSPP |
: |
Its main task is to compute the receiver clock corrections |
| SNGDIF |
: |
This program creates the single differences and stores then in
files (OBS-MAX rategy). |
| MAUPRP |
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The main task of the program is the cycle slip screening |
| GPSEST |
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The main task is Least Square Adjustment The output of this program gives the baseline length and coordinates
precisely. |
| ADDNEQ |
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This program combines the normal equations from different sessions
and gives the final solution. |
- Main Features of Bernese Software:
- Meets highest accuracy requirements
- Processing of all principal observables recorded by high precision geodetic receivers (code and phase data on both carriers)
- Five different linear combinations of L1 and L2 may be used
- Processing and combination of data from various receiver types in the same processing step (including establishing and use of receiver type specific antenna phase center variations).
- Single and dual frequency data may be processed in the same estimation step, use of ionosphere models to minimize impact of ionospheric biases on station coordinates)
- Processing of all static GPS applications
- The parameter estimation programs may be used for baseline in campaign and multiple campaign processing. Many different complex solutions (e.g. annual coordinate and ERP solutions) using (e.g. daily) normal equation systems can be produced without reprocessing observations
- RINEX data interface
- Simultaneous solution for a large number of different parameter types (Hugentobler, et.al., 2001)
Field Data Collection
The GPS data used for this study is collected in Bhuj region for earthquake studies. The GPS team from IIT Bombay carried out GPS observations during 2001 and 2002, in the earthquake affected area in Bhuj region, Gujarat, in order to understand the post-earthquake crustal deformation pattern and to monitor any future crustal dynamics in this region. The existing geodetic control network in the earthquake affected Bhuj region consists of several geodetic stations at approximately 20-40 km spacing, of the series of the Great Trigonometrical (GT) Triangulation Network of India. These series had been established during the mid-nineteenth century. GPS observations at these stations would yield valuable data about the crustal deformations in the region due to various causes, including the earthquakes of 1919 and 2001. Immediately after the 26th January Bhuj earthquake, the GPS field campaign was carried out in February 2001. A total 14 stations, including 5 old GT stations, which were found intact, and 9 new stations established close to the GT stations found destroyed/disturbed, have been observed. Four 4000SSi Trimble dual frequency geodetic GPS receivers were used for this purpose. The observations were carried out in four campaigns with 48 hours of continuous observations at every station. In February 2002 the team carried out repeat observations of all the stations in the Bhuj region.
Results and Discussions
A detailed comparison of the post-processed results of GPSurvey, Trimble Geomatics Office (TGO) and Bernese has been carried out. The baseline lengths and the respective Root Mean Square (RMS) values of baselines between the stations using the above software are given in Table 1. In Table 2, the Cartesian coordinates of different stations on WGS-84 datum, estimated using these software, are given.
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