Modelling forest cover attributes as continuous variables in a regional context with Thematic Mapper data
We modelled forest vegetation attributes as continuous variables across western Oregon using a multi-image mosaic of Thematic Mapper (TM) data. Four specific attributes were modelled using regression analysis: percent green vegetation cover, percent conifer cover, conifer crown diameter, and conifer stand age. Reference data for the cover and diameter attributes were derived from airphotos, and existing agency polygon databases were used for stand age. We developed and applied a new method for regional mapping called applied radiometric normalization. The method involved development of a set of models for a centrally located 'source' scene which were then extended to 'destination' scenes (neighboring scenes in the TM mosaic). Use of airphotos and existing digital databases in combination with applied radiometric normalization translates to a cost-effective procedure for regional mapping with TM data. Modelling forest attributes as continuous variables enables creation of a flexible forest cover information base, containing important fundamental building blocks for a variety of related classification schemes.