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3.4 Results 
  
3.4.1 Handling of the Recording Systems 
The low resolution camera Rollei CS1 is a low 
cost camera which is easy to handle. The arising 
amount of data (approx. 0.4Mbyte per image with a 
resolution of 768 x 512 pixels) can easily be 
processed with a PC. The image acquisation with 
this camera was done in short time (approx. 30 
seconds per image incl. filter changing, 
adjusting focus and aperture and image storing.) 
A disadvantage can be seen in the low resolution 
which only allows a detection of coarse 
structures. 
With the RSC, the size of the scanned pixel is 
selectable from 10um to any lower resolution. An 
additional advantage is the possibility of 
focussing without the necessity of changing the 
interior orientation, especially when further 
photogrammetric evaluations have to be effected 
with these images. The RSC thus allows a very 
flexible selection of parameters (aperture, 
sensor-gain, focus,  pixelsize, size of the 
scanned area) for every application. A 
disadvantage of the RSC, which is also true for 
other systems using a scanning sensor, can be 
seen in the relatively long time necessary for 
receiving images. For this time constant 
illumination conditions are required. 
Advantages similar to the RSC are given for the 
digital images, which originate from the scanning 
of photos acquired with the Rolleiflex 6006 
metric. Also with the réseau scanner RSi, a 
digitisation with a selectable pixel size is 
possible. Film deformations can be taken into 
account by measuring the réseau crosses 
[Sinnreich 1989]. From the same photo, digital 
images with different resolutions could be 
derived, a fact which is highly useful for 
studying the impact of resolution on the 
evaluation quality. A disadvantage must be seen 
in the difficult image acquisition which cannot 
be controled in the on-line mode. Further 
disadvantages are the delay between image 
acquisition and evaluation as well as the 
relatively high costs for the entire system. 
Nevertheless, the best results were obtained with 
exactly this system. 
Advantageous for a successful evaluation was the 
possibility given with the on-line systems to 
control the results of image acquirement 
directly. It was thus easily feasible to react 
very flexibly on changing illumination and the 
different filter reactions. With the film camera, 
it is very difficult to find the right adjustment 
of aperture and exposure time for the different 
filters. 
3.4.2 Multispectral Analysis 
Until now there was only a evaluation of parts of 
the data. So the derived results are partly 
preliminary and allow no generalization. Results 
of sooner investigations can be confirmed 
[Grunicke et al., 1990]. The following 
conclusions can be drawn: 
- It is possible to distinguish between different 
building materials. 
- For the different materials, a classification 
of damages was possible, the correlation of the 
determined classes to other materials is not 
possible. 
- On account of correlations between the images a 
selection of some filters well distributed over 
the examined spectral band leads to similar 
results as the evaluation of the synthetic 
channels of a principal component transformation 
from all channels. 
- For the examined object, a target size of 2 cm 
X 2 cm was sufficient for the evaluation. 
- Classification results of the digitised 
analogous photos and of the CCD-Cameras are well 
comparable. 
- The results from the evaluation of both 
recorded areas of the building are comparable. 
4. CONCLUSION AND FUTURE ASPECTS 
The results of the multispectral image recording 
allow different conclusions and lead to further 
studies. 
- The use of simple CCD-Cameras for multispectral 
image recording is suitable for a wide range of 
applications. 
- It is possible to distinguish between different 
building materials and to determine damages. 
For the improvement of the method, further 
studies have to be made: 
- A detailed analysis of characteristics of 
different materials, comparable to similar 
analysis in remote sensing, seemes to be useful 
for the determination of applicable combinations 
of filters and sensors. 
- Radiometric calibration of the used sensors or 
radiometric corrections of the digital images 
seem to be helpful if the illumination changes. 
- An extension of the applicable spectrum into 
others (for example the thermal infrared or the 
microwave region) gives more information. 
- The algorithms for the image processing, espe- 
cially for the classification of the data, have 
to be adapted and optimised for the special 
requirements of close range applications. 
In general, the facilities of digital 
multispectral image acquisition and evaluation 
offer a large potential of applications. 
Especially in combinations with the 
photogrametric methods of geometric evaluation 
the digital multispectral image data will become 
more and more useful for a complete analysis of 
the quality and geometry of an object. 
5. REFERENCES 
Asperen de Boer, van J. R. J., 1970. Infrared 
Reflectography. Central Research Laboratory for 
Objects of Art and Science, Amsterdam (NL). 
Grunicke, J. -M., Sacher, G., Strackenbrock, B., 
1990. Image Processing for Mapping Damages to 
Buildings. Lecture, held at the CIPA Symposium 
Krakau. 
Haberäcker, P., 1989. Digitale Bildverarbeitung, 
Grundlagen und Anwendungen. Carl Hanser Verlag, 
München, Wien, pp. 248 - 292.