Mangrove expansion is interpreted from the resulting pictures
as differences in mangrove forest edge and area between
the two successive dates. Between 40 and 80 perpendicular
lines were drawn between the two edges and progression
was measured from these lines as distances between 1966
and 1997 for Satun and Nakhon Si Thammarat and from
1967 to 1998 for Pattani and Ranong.