ERS-2 and ENVISAT radar imagery supplemented the Landsat 7 Built
classifications, and were used primarily to detect small settlements at
the periphery or outside of traditional urban and village areas and to
provide additional discrimination in the arid environments. Steps for
creating the Built radar products are described in Benza et al.,
submitted for publication and shown in Fig. 6. Manual editing was performed
to remove false detection of Built (most often associated with
high magnitude returns from localized terrain features). Radar and
Landsat-based Built classification products were merged (Built in the
30 m map product if either product indicated Built) to create a potentially
Built class for both 2000 and 2010. In addition, a rule was introduced
into the classification process requiring 2000 pixels classified as
Built to remain as Built in 2010, since any other outcome is highly
unlikely.