A STUDY ON POTENTIALS OF LOW DISTORTION MAP PROJECTIONS FOR THAILAND

Abstract

The Universal Transverse Mercator (UTM) map projection is the industry standard and being used for design and construction in Thailand. The UTM projection could introduce high linear distortion up to 965 ppm with the UTM zone over Thailand. Large linear distortion has to be properly applied and is not negligible for all steps during design and construction. To avoid these problems other countries are using alternative Low Distortion Map Projection (LDP). In this study we try to design appropriate LDPs for provincial or ad-hoc construction projects over Thailand. The design of provincial LDP is aiming, that the combined scale factor (CSF) will be less than 20 ppm. This study reveals that 58 Thai provinces, whose LDP could cover over 80% of “urban area”. The applicable LDPs are Transverse Mercator (TM) for 34 provinces, Lambert Conformal Conic (LCC) for 22 province and Oblique Mercator (OMC) for 3 provinces. The remaining 22 provinces are quite large, have mountainous topography and lot of people is living in the hills and mountaings. Trying to fit LDPs for these large provinces results linear distortion larger than 20 ppm with maximum value 229 ppm. The results of the study concludes that provincial LDP standard for design and construction in Thailand is technical possible and very encouraging. For the remaining 22 provinces we could be dividing them in to small parts and should define LDP complete for the whold Thailand.