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WCPS-Tutorial / Combining coverages

Sometimes combining several coverages within one evaluation step is required, for example, when mask overlaying is performed: both target image and mask constitute coverages. To this end, for loops can be nested. The semantics is straightforward: each loop visits the coverages listed in turn, hence every combination (actually the cross product of all coverage sets) is inspected.

Example: "the number of vegetation pixels in Landsat scenes s1, s1, and s3 within the region marked by mask r."

for s in ( s1, s2, s3 ),
    r in ( r )
return
	count( ((s.0-s.1)/(s.0+s.1) > 0.6) * m )

The result consists of three integer numbers indicating the degree of vegetation.

See manual: coverageListExpr