Investigation of the Efficiency of Multi-purpose Gravity Network of NCC to Precise Geoid Determination, Case Study: Northwest Area of Iran

The national height system of Iran, orthomertic height, is referred to geoid as the vertical datum. Consequently, the geoid has many important applications in engineering. The slow, laborious and expensive orthomertic heights can be obtained in sufficient accuracy level from geodetic height (derived by GNSS observations) and a precise geoidal height. Over the past two decades, the gravity division of national cartographic center (NCC) has developed multi-purpose physical geodesy to refinement of geoid models. In this study, the efficiency of gravity data of this network to determine of one-centimeter gravimetric geoid are investigated. In order to demonstrate geoid accuracy achievable, the simulated of high frequencies of gravity data using EGM2008 at the actual position od stations was used. Error of geoid are estimated using the Stokes-Helmert method in a closed cycle. The test area is located in the northwest of Iran, where the multipurpose network has the highest density (about 10 km). Numerical results show that accuracy achievable of geoid is about 25cm using irregular distributed multi-purpose network gravity data. Gridded data also improves geoid accuracy by up to 40%.