Document Type : Original Research Paper
Authors
1 M.Sc., Islamic Azad University, Ahar Branch, Ahar, Iran
2 Associate Professor, Geomatics College, National Cartographic Center, Tehran, Iran
Abstract
Today, with the use of Global Positioning System (GPS), it is possible to determine the geodetic height (relative to a Reference Ellipsoid) in easy mode with less time and cost. Despite of some advantages for leveling with GPS (GPS/Levelling) relative to traditional leveling, there is an important limitation which indicates the difference between Ellipsoid (as the reference datum for geodetic height) and Geoid (as the reference datum for orthometric height) named geoidal height. In order to achieve maximum accuracy in height component and then evaluating the quality results, different aspects of GPS/Levelling are considered in this study. In order to study the Feasibility of replacing precise levelling with GPS in Iran, a part of 55 km physical geodesy and geodynamic network in Azerbaijan region as well as the dense geodetic multipurpose network in Qeshm island were used. Based on different distances between each couple of points, this information, consisting of Orthometric and Geodetic heights for each point, is classified in 5 groups. The last Geoid model of Iran (IRGeoid10) with an absolute average accuracy of ±26 cm and a relative average accuracy of ±2.8 ppm are used for geoidal height. Obtained results show the accuracy of leveling height difference with GPS would be reduced by increasing the length of baseline. Index K as a criterion for determining level degree was calculated. This index shows that levelling with GPS in Iran could provide a precision of 4th degree leveling which can serve many engineering applications.
Highlights
References
Ardalan, A. A., Hatam, Y., Sharifi, M. A., Safari, A., Ghazavi, K. and Motagh, M., 2001- High resolution geoidof Iran. Technical report, NCC, Iran, 155 pp.
Gurtner, W., Beutler, G., Botton, S., Rothacher, M., Geiger, A., Kahle, H. G., Schneider, D. and Wiget, A.,1989- The use ofthe Global Positioning System in mountainous areas,ManuscriptaGeodetica, 14, 53-60.
Hamesh, M. and Zomorrodian, H., 1992, Iranian gravimetric geoid determination, second step. NCC J Surveying 6: 17-24, 52-63.
Hatam, Y., 2010- Establishment of multi-observations geodetic and gravimetric networks and determination of geoid in Iran , France, University of Montpellier 2.
Kiamehr, R., 2001- Potential of Iranian geoid for GPS/Levelling, National Cartographic Center of Iran, Geomatics 80 Conference, Tehran, Iran.
Kiamehr, R., 2006- A strategy for determining the regional geoid by combining limited ground data withsatellite-based global geopotential and topographical models: a case study of Iran. J Geoid 79: 602-612.
Kleijer, F., 2004- Troposphere Modeling and Filteringfor Precise GPS Leveling, Delft University of Technology, Netherlands,pp. 3.
Nahavandchi, H. and Soltanpour, A., 2005- High resolution geoid determination, Iranian Gravimetric geoid 2005 (IRGG05), Technical report, NCC, Iran, 121 pp.
Safari, A., Ardalan, A. A. and Grafarend, 2005-A new ellipsoidal gravimetric, satellite altimetry and astronomic boundary value problem, a case study: The geoid of Iran. J. Geodyn., 39: 545-568.
Sheng, L., 2005- The Feasibility of Replacing Precise Leveling with GPS for Permafrost Deformation Monitoring, Department of Geomatics Engineering, University of Calgery, UCGE Reports Number 20232.
Weber, G. and Zomorrodian, H., 1988- Regional geopotential model improvement for the Iranian geoiddetermination. Bull. Géod., 62: 125-141.
Yahya, M. H. and NorKamarudin, Md., 2007, The impact of tropospheric delay towards the accuracy of GPS height determination, Malaysia, UniversitiTeknologi Malaysia pub.
Keywords
)