Geography Reference
In-Depth Information
5.3. Results of thematic maps
5.3.1. Case of mangrove region
The final classified image presents the results of unsupervised classification obtained with
different thresholds identified above (Table 2). This result is obtained on the basis of 14 cluster
centers. Thus, the classified image traces an occupancy map of the study site highlighting 14
thematic classes whose characterization using data from field missions, old maps and the
lithographic charts, aerial photographs allowed us to establish different classes of information.
The exploitation of these data led to the realization of the space map shown in figure 14.
Detecting the number of class by this approach remains a major challenge. However, after
several experiments, we found that we could not indefinitely increase the number of classes.
Indeed, it proved that beyond a certain value (14 in this case) noted almost no more change
the final result. Moreover, for low numbers of classes, there was more of a smoothing of the
final result with a merging of small units in large.
Figure 14.
Satellite map from the mangrove region of the estuary of Douala, Cameroon
The classified image obtained from the 14 threshold and observing the color code (Table 2)
is shown in Figure 14. This classification method belongs to the family of unsupervised
classification. Indeed, the spectral classes are first formed. These classes are based solely on
digital information data. As a result, the classification algorithm presents below is used to
