با استفاده از داده هاي ارتفاعي دقيق TOPEX/ POSEIDON ارزيابي داده هاي ارتفاعي ماهواره

Evaluation of Topex/ Poseidon Altimeter Data Height Using Accurate Elevation Data

The purpose of an altimeter is to make accurate and precise measurements of surface height. Height refers to the distance of the surface above a reference and is computed from satellite altitude and altimeter range. In order to fully assess the accuracy of the altimeter measurements, accurate ground height data in a digital formal and with a sufficient coverage are required to compare with the altimeter height data. Ideally height values are needed to be better than the expected precision of the altimeter. The only satisfactory way to compare Radar Altimeter ( AR) data with accurate co- ordinate data is comparing the calculated RA height data with the available accurate data on a point by point basis. To compare the height data all data should be on the same datum which means the same ellipsoid. However, the map will be referenced to local sea level rather to an ellipsoid and geoid. In the case when different datum levels are used this makes a comparison difficult and it is best to look at the height difference changes.