In: Wagner W., Szekely, B. (eds.): ISPRS TC VII Symposium - 100 Years ISPRS, Vienna, Austria, July 5-7, 2010, IAPRS, Vol. XXXVIII, Part 7B 
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generation, flattening, filtering and coherence generation, phase 
unwrapping, orbital refinement, phase to height conversion and 
geocoding steps have been performed step by step and DSM of 
TSX HRS mode SAR image-pairs has been obtained (Figure 4). 
combination of HH and VV polarization the image 
interpretation is improved (Jacobsen, 2008). 
Figure 6. IKONOS DSM, grey value and color coded 
Figure 4. TSX SL DSM, grey and color coded presentation 
The world's first commercial very high resolution optical 
satellite IKONOS (means image in Greek) was launched to 
space in 1999 by Geoeye, USA. It has panchromatic and 
multispectral sensors and is able to take images with a ground 
resolution of 0.82m (PAN) and 4m (MS) with 11.3km swath 
width from 681km orbital altitude. By the combination of both 
sensor products lm pan-sharpened color images can be created. 
The more than 300 million square kilometers of imagery that 
IKONOS has been collected over every continent; they are used 
for national security, military mapping, air and marine 
transportation, by regional and local governments and others 
(URL 2). 
Figure 7. Multi-polarization (HH/VV) TSX SL image from the 
city of Dresden 
In this study, in Istanbul test field, PAN IKONOS GEO stereo 
model with a ground sampling distance (GSD) of lm was 
available. The height-to-base (h/b) ratio value was 1.6 (angle of 
convergence 35°) and the sun elevation angle is 65.5° (Alobeid 
et. al., 2009). Using this stereo model DSM have been 
generated in 3m grid spacing overlapping with test field and 
with the refinement processes (shifting, blunder filtering etc.) 
regulated for the evaluation analysis. Figure 5 shows the 
IKONOS stereo-images and figure 6 illustrates the generated 
DSM along with its color coded version after the refinement 
process. 
Figure 5. High resolution IKONOS PAN images 
Against optical images, SAR images have some speckle effects 
which can be reduced by filtering but this causes also a loss of 
information. On the other hand some special objects like 
railroads with the metallic rails can be seen clearer like in 
optical images. The information contents of SAR images can be 
improved by multi polarization like shown in Figure 7. By the 
The reference DEM was derived from 1:1000 scale digital aerial 
photo grammetric maps, a project of Greater Istanbul 
Municipality and involves the large part of Historical Peninsula 
and near surroundings. This DEM was generated between 2007 
and 2009. The original grid spacing of the DEM is 5m but it has 
been resampled into lm according to the needs of the project. 
Figure 8 illustrates this reference DEM along with colored 
version to visualize the elevation levels easier. 
Figure 8. High resolution IKONOS PAN images 
This DEM overlaps with the test field, approximately 5km><5km 
and covers more than 95% built-up areas that’s why accuracy 
analysis were not performed for open and forest areas 
separately. It has 10cm up to 1 m accuracy and the elevations are 
in between sea level and 90m. This reference DEM is named as 
‘REFDEM’ in the study.