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

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IV - BURNED LAND MAPPING, FIRE SEVERITY DETERMINATION, AND VEGETATION RECOVERY ASSESSMENT
sensor TerraSAR-X ERS ASAR
dataset 16 Nov 08/19 Dec 2008 28/29 Mar 96 08 Jan/12 Feb 09
polarization HH HV HH&HV VV HH
local inc. angle R 2 R 2 R 2 Std. err. R 2 Std. err. R 2 Std. err.
all pseudo-plots 0.631 0.303 0.692 197.7 0.651 153.5 0.435 269.7
pseudo-plots grouped by local incidence angle
10-15 - - - - 0.655 149.9 0.864 132.0
16-20 - - - - 0.662 152.3 0.819 149.3
21-25 0.936 0.768 0.936 101.5 0.746 132.5 0.732 173.4
26-30 0.861 0.551 0.866 126.1 0.741 130.9 0.712 176.7
31-35 0.678 0.368 0.717 178.8 0.735 135.8 0.648 203.1
36-40 0.685 0.380 0.702 175.6 0.743 125.3 0.711 200.3
41-45 0.652 0.381 0.653 197.2 - - - -
46-50 0.732 0.499 0.732 181.0 - - - -
51-55 0.727 0.391 0.748 164.9 - - - -
56-60 0.854 0.594 0.854 140.0 - - - -
66-65 0.862 0.478 0.865 129.2 - - - -
Table 1 - Determination coefficients explaining the agreement between burn severity and
interferometric coherence.
5 - Discussion
Figure 1 shows that coherence increases with burn severity at all frequencies
and polarizations. However, noticeable differences in absolute values
appear not only between data acquired at different SAR frequencies but
also for image pairs acquired with the same system at different time interval.
Coherence increased by about 0.25-0.3 units from unburned to highly
burnt forests. Regression analysis showed moderate relations between dNBR
values and interferometric coherence of co-polarized beams when local
incidence angle was not accounted for. Determination coefficients were
highest for X-band and one-day C-band data (Table 1). The use of the coand
cross-polarized X-band coherence in the regression model did not
improve significantly the results. Analysis of dNBR as a function of coherence
after grouping by 5 0 local incidence angle intervals showed increased
values of the determination coefficients for all frequencies and polarizations.
Coherence was affected by topography, decreasing with the increase
of the local incidence angle (Figure 2).
6 - Conclusions
Interferometric data provided important advantages over the use of
backscattering coefficient for burn severity evaluation: i) lower influence