The geodetic datum transformation is still an important issue specially these days where GPS is used extensively. In Egypt and many other countries, obtaining an accurate-consistant transformation parameters set is not an easy task. This is because of the inaccuracy and inconsistency in the local geodetic networks. In Egypt, the first order triangulation network is adjusted many times in the university researches. More accurate coordinates than those of the Egyptian Surveying Authority (ESA) are obtained. The adjusted coordinates are also used in computing better transformation parameters. The adjusted coordinates are not adopted in ESA because the whole surveying works in Egypt for about 70 years are based on ESA coordinates. Therefore any better transformation set are not used because it produces transformed coordinates do not match the corresponding coordinates in ESA. In this research, local adjusted coordinates are used in the transformation process to be done in more accurate atmosphere. Then the resulted transformed coordinates are modified to match their corresponding values in ESA. The followed procedures are done in such (remove – transform – restore) process. This process improved the transformation results significantly while the resulted coordinates are still belonging to those of ESA. It is known that the Egyptian triangulation network consists of two main parts and the precision of their coordinates are different and not constant allover the network. The available GPS coordinates are also different in their precision according to the way of collecting and processing the data. So, the effect of using weights in the transformation process is also investigated in this research.
|
