Salami, Ayobami T.
Table 2: Separability Percentage Index of Cover Types
Cl C2 C3 C4 C5 C6
Ci 0.00
C2 99.88 0.00
C3 99.87 83.81 0.00
C4 89.79 83.15 84.69 0.00
C3 100.00 100.00 90.99 99.58 0.00
C6 100.00 99.96 99.75 96.79 27.93 0.00
NOTE: C1-C6 are as defined in Table 1.
4.2 Confusion Matrix
Confusion matrix (Table 3) depicts the extent of homogeneity of the cover types. It shows that burnt
patches were 90.70% homogenous. The class has 5.43% overlap with mixed grassland. This overlap could
be due to the fact that method of land preparation in the area includes clearing and burning of the vegetal
cover, and the Landsat scene was recorded during the period that farmers in the area usually prepare the
groud for cultivation. It might also be due to the fact that mixed grassland contains some elements of burnt
patches.
Table 3: The Confusion Matrix
Cl C2 C3 C4 C5 C6 RJ TP
Cl 90.70 0.78 0.00 5.43 0.00 0.00 3.10 100.00
C2 0.00 91.30 4.78 2.61 0.00 0.00 1.30 100.00
C3 0.00 4.81 93.17 721 0.00 0.00 4.81 100.00
C4 4.61 2.52 6.38 81.83 0.00 0.24 4.42 100.00
C5 0.00 0.00 0.00 0.12 83.42 15.24 122 100.00
C6 0.00 0.00 0.00 2.55 37.82 54.01 5.60 100.00
NOTE: C1-C6 are as defined in Table 1.
RJ- % of rejected or unclassified pixels.
TP- Total %.
Arable cropland/fallow complex was 91.3% homogenous. The class has 4.78% confusion with exposed
land/settlement and 2.61% overlap with mixed grassland. This means that some portions of this cover type
has been exposed due to cultivation while grasses are growing in some parts. Exposed Land/Settlement was
83.17% homogenous. It has 7.21% overlap with mixed grassland and 4.81% confusion with
cropland/fallow complex. This confusion is not abnormal as some parts of the cropland and mixed
grassland in the area were exposed as a result of cultivation and grazing respectively.
Mixed grassland was 81.83% homogenous. However, elements of this cover type were found in all but one
of the classes. This result confirms the classification of the study area as forest-savanna transition zone by
Adejuwon (1971). Mixed grassland has 6.38% overlap with exposed land/settlement, 4.61% with burnt
patches, 2.52% with cropland/fallow complex and 0.24% with young secondary regrowth. It was noted
from the confusion matrix that elements of mixed grassland were not found at all in tree cropland/mature
secondary regrowth while they are rarely present in young secondary regrowth, which is actually fallow at
an advanced stage of succession. This result implies that it is the opening of the mature forest in the area for
cultivation that encourages the growth of grass. Grass could therefore not be said to be a natural habitat of
this environment. This finding confirms the submission of Adejuwon and Adesina (1988) that regressive
succession is already in progress in some parts of the Tropical Rainforest belt of Nigeria. Tree
cropland/mature secondary regrowth was 83.42% homogenous. It has 15.24% overlap with mixed
grassland.
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International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B7. Amsterdam 2000.