Precise and Minimum Bias Transformation

The Geographical Survey Institute (GSI) constructed the new geodetic datum of Japan, “Japanese Geodetic Datum 2000 (JGD2000) ”. The coordinates of the old geodetic datum of Japan, “Tokyo Datum (TD) ”, should be replaced by JGD2000. This report proposes precise and minimum bias transformation for the public and cadastral survey networks. Least squares collocation method is used for the precise transformation. To minimize a network bias, the transformation parameters are calculated over a small area every year. The transformation keeps the network configuration constant.“TKY2JGD”software is published by GSI to transform the coordinates from TD to JGD2000. This report also proposes that transformation distortion of the TKY2JGD can be estimated by applying the strain theory. The distortion of transformed coordinates is expressed by angle and scale changes. The angle and scale changes correspond to the maximum shear strain and dilatation respectively.