A similar study was performed to derive geoidal heights from precise trigonometric
heights across the city of Istanbul/Turkey which extends over a pretty rugged area
(SOYCAN 2006).
For the aim of this study, applying terrestrial levelling techniques over slopes
and rugged areas are somehow cumbersome since the surveying takes time and the
accuracy is degraded. This study shows results from an experiment especially
designed to show the performance of GNSS height determination over slopes in the
case of multipath error. To show the applicability of the method results are
compared with trigonometric levelling and geometric levelling. Furthermore, the
results of several test trials concerning various data sampling and GNSS analysis
strategies are presented. Thorough investigation is undertaken on multipath that is
effective on one of the points used in the scope of this experiment since it is the
primary error source on results.
2. DESCRIPTION OF THE EXPERIMENTS
The experiments were performed in the Samandira region, Istanbul, Turkey.
The geographic location of the studying area can be seen from Figure 1. In order to
provide information on the a topographic model of the region, the ground elevation
data (a digital terrain model) is presented in Figure 2. The digital terrain model
(DTM) is based on the satellite images. The obtained data from the GIS Department
of Istanbul Metropolitan Municipality, has been used for creating the maps and
DTM of Istanbul. It gives the information on steep slopes at the studying area.
Figure 1 - Geographic location of the studying area.