A Sub-Area Fitting Approach for GPS Height Conversion

GPS height conversion into normal heights has become a hotspot in survey engineering. Many Researches and applications have proved that the Quasi-geoid surface can be very complicated especially in a large survey area or in complicated terrain, just adopting several GPS/leveling points to construct quadric surface model to fit the Quasi-geoid surface has some limitations, precision could not be guaranteed. So, such demand us that we should partition large survey area into several small one as possible especially in complicated area, and then fit the Quasi-geoid surface. So, the paper put forward a kind of sub-areas fitting approach for GPS height conversion, firstly, remove high precision of long wavelength contributions from GPS/leveling points, secondly, draw the surplus isolines of quasi-geoid value, which is compared to the isolines of quasigeoid value in the experiment, the number of convexities or concaves could be seen, and the results showed that the approach is much valid and something useful is obtained.