Changing Horizons in Geography Education - HERODOT Network ...

Table 1. NDVI-classes and their correspondence with the ground truth Classification of theName NDVI-values Ground truthmulti-spectral images(Landsat, SPOT andNDVI0 -1.00 to -0.60 burned and post-burned areasASTER) was basedNDVI1 -0.59 to -0.20 villages, fields and bare steppeon the NDVI-valueNDVI2 -0.19 to 0.00 steppe(Normalised DifferenceNDVI3NDVI4NDVI50.01 to 0.200.21 to 0.400.41 to 0.60regenerated steppe“foret claire”“palmerais faible” and “foret galerie”Vegetation Index)(Lillesand, Kiefer, 1994,pp. 506−507).NDVI6 0.61 to 0.80 “palmerais faible” and “foret galerie” T he N DV I-valuewas calculated for allNDVI7 0.81 to 1.00 “palmerais dense”multi-spectral imagesclouds digitised clouds and cloud shadowand a slicing techniquedivided the different NDVI-values into eight classes as shown in table 1 and Figures2 and 3:Figure 2. NDVI-classified SPOT imageFigure 3. NDVI-classified ASTER sceneNDVI-classification was impossibleon the Corona image. Therefore threeclear vegetation categories were interpretedand digitised (Figure 4): ‘palmerais’,‘forêt galerie’ and ‘forêt claire’.Comparison of the classif iedimagesVegetation dynamics can be visualisedand interpreted using multi-temporalcolour composites. For this it is advisableto create binary images first, whichundoubtedly facilitates the interpretationof the composite. These binary92Figure 4. Digitised Corona mosaic