Black and white and true-colour aerial photography from 2004, 1993 and 1985 are used for studies of growth and change of informal
settlements in Voi, SE-Kenya. The digital data is orthorectified, corrected for brightness variations caused by light falloff and bidirectional
effects and mosaicked using EnsoMOSAIC and Erdas Imagine software. The constructed mosaics are segmented with
eCognition software and classified to built-up and non-built areas, in order to produce a mask of structures, which will be extracted
into vector format. A post-classification comparison change detection in building-level will be done with ArcView software between
all three masks. The work is still under way, but some preliminary results are given.