Timber age verification using historical satellite image analysis

Timber inventory data is important for estimating the net present value (NPV) of timberland sales among paper companies, timber investment and management organizations (TIMO), institutional investors, and individual investors. Timber age in an inventory GIS database can be quickly verified through a series of historical satellite image analyses based on image differencing techniques. The normalized difference vegetation index (NDVI), tassel-cap greenness, wetness, simple differencing of band 5, and a vegetation conditions index were used collectively as an individual change detection index, and simple averaging was employed in the integration of individual results. With respect to timberlands of more than 200,000 acres in the states of Washington and Oregon, harvest years from satellite image analysis and timber ages in the inventory GIS database were compared, and the areas of age mismatch were summarized for field verification. This practice is not a complete solution for inventory verification, but it can reduce significant time in on-site verification by effectively offering a list of potential age-discrepancy tracts. With the support of fieldwork confirmation, the proposed practice can be a very effective and efficient means of practicing due diligence for timberlands in the forestry industry.