The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part Bl. Beijing 2008 
1106 
4.2 Testfield Sakurajima, Japan 
The Sakurajima testfield for DSM generation is a steep 
volcano area. A small part of the volcano Sakurajima is given 
as a laser scanner reference dataset provided by Kokusai 
Kogyo Co. Ltd. with a resolution of 5 m. Figure 5 shows the 
orthophoto together with the extension of the reference area. 
The main characteristics of the volcanic area results in the 
following matching conditions: a large part of the area of 
interest is covered by heavy shadows without any useful grey 
value information and a large part has also no sufficient 
texture (e.g. the caldera). Good texture suitable for image 
matching is only available along the edges of the shadows. 
In the PRISM triplet, the larger one of the two craters is 
covered by clouds. This area was defined as a dead area, no 
height values where determined for this areas and by this it 
was excluded from the evaluation. 
The Root Mean Square Error (RMSE) of the triangulation is 
in planimetry and height below one pixel for the Direct 
Georeferencing Model (DGR) see Kocaman and Gruen 
(2008). 
Figure 5. Sakurajima: Orthophoto (Nadir) and the extension 
of the reference area. The black area is a cloud area which 
was excluded from the evaluation. 
# points 
RMSE-Z 
Mean 
Min 
Max 
394828 
10.8 m 
-0.71 m 
-111 m 
60 m 
Table 2. DSM accuracy evaluation results of the test area of 
the volcano Sakurajima. 
Figure 6 shows the color coded DSM of the mountain area 
around the volcano. Table 2 summarizes the evaluation 
values of the DSM generation. The height RMSE is better 
than 5 pixels (10.8 m). The quality of this DSM generation is 
mainly influenced by the large part of shadow areas without 
sufficient grey value information for a suitable image 
matching. In these areas we have blunders up to 100 m. To 
visualize this influence 
Figure 7 
Figure 6. Shaded and color coded visualization of the 
generated DSM of the volcano. The black area is a cloud 
defined as dead area without any height information. 
Figure 7 shows the analysis of the DSMs for a shadow area 
marked in Figure 5 (green square). 
Profile Reference DSM Laser Scanning 
1,020-IT 
1.000-^^ 
980 
0 50 1 00 1 50 
Figure 7. Profiles of the DSMs for the same area and their 
evaluation results. 
On the left side we have first of all the profile of the 
reference DSM with small structures of the volcano surface. 
The second profile on the left side is generated for a 
DSMp 0 i nts generated by using only feature and grid points. 
The third one results out of the DSM lines , when only lines 
were used for the DSM reconstruction. The first image on the 
left side is the original nadir image of the shadow area 
with the position of the profile line. The last two images on 
the right sight show the profiles of the height errors 
(reference DSM - generated DSM) for DSM points for DSM lines . 
There are big blunder areas up to - 80 m in case of DSM points 
and up to - 57 m in case of DSM lines . For the reconstruction 
of DSM po i nts , mismatched points were found inside the 
shadow area. In case of DSMi mes lines were matched only at