Transformation between Local and UTM coordinates using LIDAR height data interpolation (Case study: Isfahan

Coordinate systems transformation has an important role in mapping activities, geodesy and spatial science. New and efficient methods are needed in order to increase the accuracy in the transformation between these systems. The main purpose of this article in the first part, is a local coordinates transformation in Isfahan City to UTM coordinates
and vice versa. This method is based on the combined scale factor. So, the coordinates of 500 GPS stations in Isfahan City was used,and with reduction of distanceson the surface of the earth to the map, coordinates of the GPS points in the local system was calculated.Study on changing of combined scale factor for the GPS points of Isfahan City shows that if a unit scale factor is used for whole the city, in long lengths occurs a few decimeter differences and it is not suitable for accurate mapping. LIDAR is a mature remote sensing technology which can provide accurate elevation data for both topographic surfaces and above-ground objects. So in the second part of the article, we presented an algorithm to provide height interpolation for the points in the passage network of Isfahan City by using LIDAR data,because the inverse transformation from local system to UTM using new methods such as Rational Functions, needs vertical component in addition to horizontal position of points. A height bias of 30 centimeter has been detected in the LIDAR data using GPS control points. After removal of this systematic component, the final RMSE of LIDAR heights are 43 centimeters.