INTRODUCTION 
An understanding of the consistencies and changes in settlement detection ability 
related to radar system and environmental parameters is of potential interest to diverse 
segments of the scientific community. On one hand such data can supply useful input to 
environmental monitoring efforts and population assessments at many levels--particularly 
where such information is dated or absent. Settlement detection and data inferred from 
such data (e.g. population estimates, urban growth models) are important factors and 
desired by many resource management users--especially those in developing nations. On 
the other hand the correlations between urban morphology (structure characteristics) and 
changes in radar signal response are of interest to scientists attempting to define and 
model the theoretical nature of system-target relationships and specular reflection 
parameters relevant to semi-automated interpretation techniques. 
In this experiment SIR-B imagery of central Europe was examined to explore the 
influence of incidence angle, look direction, and environment- 
terrain conditions on settlement detectability. Although previous efforts in this regard 
have contributed to an eclectic collection of data, few have been able to employ multiple 
images of the same area. Using airborne K-band imagery of five New England study areas 
Simpson (1969) found that 100 percent detection was possible for cities over 7,000 
population. Henderson and Anuta (1980) examined K-band and X-band airborne imagery of 
diverse areas in the United States as well as one Seasat-SAR (L-band) image of central 
Pennsylvania. With the former imagery a scale of 1:200,000 was determined necessary to 
attain consistent detection of settlements with a population of at least 1,000. However, 
only a 68.3 per cent accuracy for similar size settlements was attainable with the 
low-incidence (ca 21-23 degrees) angle Seasat Image. Drake and Patton (1980) stated it 
was difficult to identify towns on Seasat imagery of the Delmarva peninsula as the signal 
return was similar to that from agriculture and forest vegetation. The specular returns 
from settlements were found to be similar to and confused with such structures as poultry 
barns. 
Dowman and Morris (1982) were able to detect around 16 per cent of isolated rural 
buildings, 37 per cent of houses, and 70 per cent (HH polarization) and 87 per cent (HV 
polarization) of high rise buildings using X-band imagery of an area west of Ottawa, 
Ontario. Plotting of more recent residential developments was more successful than of 
older areas. Seasat SAR L-band imagery of four U.S. urban areas (some with two 
different look directions) was used by Hardaway, et.al. (1982) to explore cardinal effects 
of urban structures. Streets/houses at angles of 20 degrees or less from perpendicular to 
the radar look direction were found to accentuate radar echoes, but there was no apparent 
relationship at greater angles.