7th Workshop on Forest Fire Management - EARSeL, European ...

Fuel type mapping using SPOT-5 imagery and object based image analysis 71
3.2 - Field measurements and fuel classification scheme
The Prometheus classification system was adapted to the vegetation conditions
of the study areas and 9 fuel type classes were created: i) rural/no
vegetation areas, ii) agricultural areas, iii) very sparse vegetation, iv)
sparse shrublands, v) dense shrublands, vi) sparse broadleaves, vii) dense
broadleaves, viii) sparse conifers and ix) dense conifers. Homogenous
patches (30x30m), representative for all fuel conditions, were located using
GPS device and extensive field measurements were collected both for training
and assessing the classification process. Stratified sampling method
was used to select the samples. Main vegetation species, species composition,
canopy cover and density, terrain information were recorded for every
sampling area.
Figure 1 - a) Study area of Chalkidiki and b) Study area of Attica.
3.3 - Satellite data preprocessing and image enhancements
All SPOT5 images were orthorectified using the mosaic of the B&W
orthophotographs and the 20m DTM. Due to the temporal difference of their
acquisition, radiometric enhancement (histogram match) was performed to
all SPOT5 images. Two mosaics were derived from the enhanced data. NDVI
values were calculated and integrated to them.