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

Assessment of spectral indices derived from modis data as fire risk indicators in Galicia 111
based on a bibliographic compilation of different works that have used
these indices as indicators of the vegetation conditions. As shown in
Sánchez et al. (2009), the fire frequency is represented versus the variation
suffered by the indices during de previous period.
The 50% of the data (odd years) are used for obtaining the relation, and
the other 50% (even years) for the validation.
4 - Results and discussion
From the previous analysis, only three of the indices were shown to fit a
linear regression, these are: EVI, GEMI, and SAVI. Figure 1 shows the linear
regression of these three indices.
Figure 1 - Linear adjustment between the percentage of fire-affected cells and the index variations
in the previous two weeks, for odd years.
For the validation we use the even year data. We apply the equations
obtained for each index to the variations suffered by the index, and compare
the results obtained with the real fire data. Results of these adjustments,
as well as a statistical analysis are included in table 1. Based on
these results we conclude that both, GEMI and EVI, can be used to estimate
the fire probability in a cell with an error about 15%.
The organisms for the management of fire prediction and extinction tasks
use graduated scales for fire risk prediction. After some proofs we observed
that the most optimum classification is: High risk (∆index