Malaimani, E.C.: Estimation of Very long Base Lines by GPS -Geodesy for Indian Plate Kinematic Studies. - Bonn, 1999. - Dissertation, Rheinische Friedrich-Wilhelms-Universität Bonn.
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author = {{E.C. Malaimani}},
title = {Estimation of Very long Base Lines by GPS -Geodesy for Indian Plate Kinematic Studies},
school = {Rheinische Friedrich-Wilhelms-Universität Bonn},
year = 1999,
note = {Under the Indo-German Collaborative, Bilateral Exchange Programme, a Project to study the ongoing Indian plate motion has been initiated between the National Geophysical Research Institute (NGRI, CSIR) and the Geodetic Institute of the University of Bonn, Germany. In this project, a permanent tracking/reference station was established at NGRI, Hyderabad by installing a Turbo Rogue GPS -SNR 8000 Receiver and the corresponding data taking and storing facilities. The GPS measurements in the IGS Global Network are meant to monitor intercontinental and intra plate crustal motion and to determine velocity vectors, eventually to derive information concerning the stresses in the Earth's crust, in particular in the Southern Himalayas. The GPS-campaigns used in the data analysis cover a time period of approximately 3 years, during which observations were taken at least twice a week. The data transfer had to be carried out off-line by mailing diskettes, which meant that the analysis had to be performed in a post-operative way. The adopted strategy was to retrieve the data from a selected set of IGS-permanent stations on the Eurasian continent as well as in Australia and South Africa.
The refined GPS data processing and analysis by using Bernese software were carried out at the Geodetic Institute. The first data set up to Jan. 1997 was prepared and a Global Network solution was carried out to estimate Very Long baselines between Hyderabad and other IGS selected stations. Subsequently, the processing of 300 epochs was carried out in a semi automatic way using the Bernese Processing Engine (BPE). Special care was taken to eliminate incomplete or otherwise defective data sets before the final run. Two different types of solutions were performed, the first one by an epoch by epoch solution which shows the time evolution of coordinates and baseline lengths, and the second one for simultaneous coordinate and velocity vector estimation. The first solution was helpful to visualize the repeatability of the results for each epoch and to derive realistic error estimates for the site motions.
In chapter 9, (Results and Discussion), we discuss the significance of the most important results achieved so far. Our processing of 3 year's data from Sept. 95 to Sept. 98 by global network solution involves estimation of baselines of 500 km (Hyderabad-Bangalore) to 7000 km (Hyderabad-Yaragadee) lengths. One important result is that the baselines up to 6000km yield quite reliable repeatabilities within 2cm. Thus, the baseline between Hyderabad and Irkutzk (Russia) is shortening at a rate of 5cm/year, with a high level of significance. The baseline between Hyderabad and Bangalore shows a compression in NNE-SSW direction over the past 3 years, yielding a first constraint for the inner plate stability of the Indian plate of 2mm/yr ± 1mm/yr. This information could gain importance in respect to the inner plate seismicity (cf. recent Latur earthquake). On the other hand, the baselines beyond 6000km suffer from reduced simultaneous visibility and, correspondingly, suffer substantial accuracy losses.
In summary, the most significant result of our analysis is that the baseline vectors from Hyderabad to other stations beyond Himalaya are shortening. This phenomenon is fitting into the basic theory of Indian plate motion. Velocity vectors thus computed for all the stations used in the analysis are comparable with the NUVEL -1A global plate model. This means that a first breakthrough in determining plate motion rates for the Indian Subkontinent has been achieved.},

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