EuroSDR Projects - Host Ireland

5.4.2 Qualitative Comparison
The railways in the north of the images were located by all interpreters (just one interpreter only
evaluated roads) and classified correctly by all SAR interpreters. Only two optical interpreters
classified them as roads. Some SAR and optical interpreters included several houses in the analysis. In
several cases, both optical and SAR images allow the detection and location of houses, even the
smaller ones. In addition some interpreters, SAR as well as optical, detected land use boundaries,
bridges, parking areas, trees and hedges. It was possible to detect them well in optical and in SAR
images.
Some undefined lines, which look like historical objects, can be found in a small portion of the SAR
image. These lines are only located in the SAR image. Three interpreters of the SAR image located
them well; the other classified this area as an undefined area. That is the reason why it is not included
in the quantitative analyses.
5.4.3 Summary – Trudering
The figures relating to the quantitative analyses show the best result of the test sites. The continuous
and large parts of agriculture and built-up areas were located and classified with best results (mostly
up to 90% correct). Even the smaller areas, such as water bodies and excavation areas were identified
with a high degree of accuracy. The interpretation of forests – usually conducted very accurately –
resulted in more failures. Some interpreters added hedges and several trees to the forest class which
might be a reason for misinterpretation. Due to the high resolution of the image data, it was possible
to detect several houses and trees comparatively well.
The detection of linear objects shows best results equally well in SAR and in optical imagery. Just the
classification of railways might be difficult, surprisingly in optical imagery. The fact, that this test
site’s data is of a high resolution leads to the best visual interpretation result among all test sites. The
accuracy and quality for SAR and optical imagery is equal, even for smaller objects.
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