Tuesday 10 July 2018 2:30pm
The School of Surveying is working with the Survey Department of Nepal on plans to carry out an extensive survey program to re-measure the height of Mt Everest after the 2015 earthquake. The program will use two independent measuring techniques in tandem. The first is conventional trigonometrical (trig) heighting where the height is measured by the angle of the summit from the horizontal relative to points of known elevation in Nepal. Using the distance of these points from the Mt Everest summit and the zenith angle, the height can be solved using trigonometry. The second technique is GNSS (GPS) where one receiver will be placed on the summit. Unfortunately these techniques give heights in different systems, ellipsoidal heights in the case of GNSS and orthometric (sea level) heights in the case of trig heighting. These techniques are related by the geoid and our knowledge of the geoid separation requires some remedial work in Nepal. In addition, before the trig heighting can be carried out, the orthometric heights for the observing points of the Mt Everest summit must be known which will require levelling to determine them. In order to determine the orthometric heights of the observing points and to resolve problems with the geoid in Nepal, the Survey Department will level from a point in southern India. This point has recently been surveyed by the Survey Department of India and thus have not been effected by the recent earthquakes. They will also make gravity measurements and GNSS on the new benchmarks established to refine the Nepal geoid model.
Through this proposal, New Zealand experts from Otago University' School of Surveying will provide technical expertise and advice to enable the Survey Department of Nepal to bring this project to a successful conclusion. In addition Trimble New Zealand will provide equipment to facilitate the GNSS part of the program.
As part of this program Dr Chris Pearson, who has been working with the Survey Department of Nepal to help repair the geodetic system after the 2015 earthquake, will spend another 5 weeks in Nepal to work directly with the Survey department staff starting July 12th.