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Theme: THE DEGRADATION OF WETLANDS AND ITS SOCIO ECONOMIC AND ENVIRONMENTAL IMPLICATIONS IN NDOP CENTRAL SUBDIVISION, NORTH WEST PROVINCE CAMEROON

visually identified on the aerial photographs. The G.I.S software, MapInfo professional 7.5 was used. Once imported in this software, the four points were marked and stored in the G.I.S data base. The projection used in georeferencing was UTM 32 N, datum WGS84 and the reference was in longitudes and latitudes. The route mean square error (RMSE) margin did not surpass 1. This process was carried out on all the photos. Since the photos were imported in different layers, opening all the layers led to an automatic mosaic of all the five photos which covered the study area. Still based on interviews and observations on the field, as well as on visual observation of the aerial photos, surfaces occupied by wetlands were calculated by using semi-supervised methods. Through this process, identical occupations were regrouped and their surfaces obtained.
Cartography of the area during this period was realised using Adobe illustrator 9.0 (a computer drawing software).

1.8.2.5 Analysis of the satellite images:

A Landsat TM image of 1988 and a Landsat ETM of 2002 image were used as the bases for this analysis. The images had the characteristics presented on table 4.
Table 4: Characteristics of satellite images for the study.

Property	Image of 1988	Image of 2002
Sensor	Landsat 5TM	Landsat 7ETM+
Scene	P187R57_5T88112	P185R05620020515
Altitude of the orbit	705km	705km
Repetition	16 days	16days
Bands	3 Bands registered under IMG format(Erdas 8.5)	3 Bands registered under IMG format(Erdas 8.5)
Coverage	185 km	185km
Spatial Resolution	28.5 m	28.5m
Acquisition Date	12/05/1988	15/05/2002
Projection	UTM32N	UTM32N
Datum	WGS84	WGS84
Units of measurement	meters	meters

Source: Global Forest Watch (2006)
The images were in colour and had the base canals of (R.G.B), see figure 3. Each colour gave the first impression of the kind of land cover e.g. the dark zones, for wetlands, the green for vegetation and the white for habitations.