VTT – Forest inventory

During the past twenty years VTT has conducted many feasibility studies including woody and other biomass assessment in many countries in Europe and beyond, particularly for energy industries and biorefineries. Although forest inventory is usually done by specifically appointed organizations, for example Natural Resources Institute in Finland, general data are publicly available in all countries in Europe. In addition, extensive networking with other research organizations enables VTT to assess the availability of woody biomass in most parts of the world.

The remote sensing team of VTT has used satellite-based optical data in producing maps of forest areas and different types of forest. The key methodological tool in these forest mapping projects is the VTT-developed Probability method. Here an unsupervised clustering is applied to the satellite image dataset. The clusters are used as classes in maximum-likelihood classification. For each class, the forest type and forest volume variables are estimated from ground data. The final estimates for forest variables are computed as weighted averages over classes using class probabilities as weights. The amount, type, and format of ground data can vary a lot.

The widest area that has been mapped is the whole Europe. It was covered with a mosaic of NOAA/AVHRR (National Oceanographic and Atmospheric Administration/Advanced Very High Resolution Radiometer) data, which has a spatial resolution between 1.1 km and 2 km. In the on-going NorthState project (EU/FP7), two test sites of 200-km by 200-km have just been mapped for forest types, forest area, and forest change (logging) with Landsat data.

The same Probability methodology can also be used in more localized forest resource mapping projects for forest industries. In these projects, the satellite image resolution has varied from Landsat (30 m) and Spot (10 m) to VHR satellites like GeoEye (multispectral resolution 2 m, panchromatic 50 cm). In addition to optical data, VTT has used satellite-based radar data (ALOS/PALSAR, Advanced Land Observing System/Phased Array L-band Synthetic Aperture Radar, resolution 20 m) for mapping forest biomass.

In addition to satellite remote sensing data, VTT has developed an interactive tool for ground data measurement in forest stands. The tool called RelasPhone (for Android devices) is available from Google Play store. Basal area is measured per tree species using a technique similar to the traditional optical relascope measurement. Tree height estimates are used to complete stand-wise stem volume measurements.