Non Parametric Approach to Transformation of GPS Coordinates into Local Datums: An Application to Indian System

This research paper presents methodology for the transformation of planimetric GPS coordinates into Indian datum, when standard transformation methods such as Helmert and Molodenskiy formulae can not be used due to non-availability of required parameters or greater inhomogenity of local datum. The planimetric coordinate transformation between two datums was taken as the rubber sheeting between less precise local datum and very precise WGS-84 datum coordinate planes. The mapping function between two planes was represented by affine mapping function for the localized area (preferably in the extent of one degree of latitude and longitude). The accuracy of map derived GCP coordinates in local datum was tested by point pair matching technique and subsequently increased analytically, by using high-resolution satellite imagery rectified with the help of differential GPS (DGPS) data. This technique may be useful for the transformation of GPS coordinates to any local datum of unknown transformation parameters. The approach presented here is particularly significant for utilizing remotely sensed imagery in local datums.