409 
Symposium on Remote Sensing for Resources Development and Environmental Management / Enschede / August 1986 
Development of a regional mapping system for the sahelian region 
of west Africa using medium scale aerial photography 
Steven J.Daus, Mamane Guero, François Sesso Codjo, Cecilia Polansky & Joseph Tabor 
Resources Inventory and Monitoring section, Forestry and Land Use Planning project, Niamey, Niger 
ABSTRACT: In response to an expressed need by the government of the Republic of Niger, a systematic mapping 
procedure was developed to determine the surface area of forest lands in Niger. The objective was to develope 
an approach suitable to: 1) the nature and value of the resources to be mapped and evaluated, 2) the available 
source, or base, data, and 3) the technical capability of the Nigérien forestry personnel. The approach 
included, regional stratification using LANDSAT MSS imagery, collection of ground data, and extrapolation of 
this point specific data to the entire study area with the aid of a photo interpretation key developed for the 
region. 
RESUME: Selon des besoins precise par le governement de la Republique du Niger une procedure de la 
cartographie systématique a était develope afin de determiner la superficie des terrains forestier au Niger. 
L’objective était de établir et mis en oeuvre un system adapte a: la nature et valeur des ressources dresse, 
les données de base disponible, et les capacitees techniques des cadres forestiers du Niger. L'approache 
compris d'une delimitation regionelle a partir des images satellites LANDSAT, collection des données de 
terrain et extrapolation des données des sites jusqu'au niveau de la zone d'etude entire aide par une clef 
standard d'interpretation des photos aeriennes. 
1.0 INTRODUCTION 
The results presented in this paper are those from 
work completed at the Resource Inventory and 
Monitoring (RIMS) section of the Forestry and Land 
Use Planning (FLUP) project. This project is funded 
under the cooperative agreement #683-0230, between 
the United States Agency for International 
Development (USAID) and the government of the 
Republic of Niger (GON). The primary aim of this 
bilateral project is to establish within the 
National Forest Service (NFS) of the GON a unit 
capable of conducting resource inventories and 
provide technical assistance regarding forest 
management practices. This unit, the Office of 
Technical Assistance (OTA), would contribute 
information and technical assistance primarily at 
the planning level within the GON. 
The RIM section was established within the 
structure of the FLUP project in order to: 1) 
develop and implement resource inventory methods 
appropriate to the various information needs of the 
GON, and 2) train GON forestry personnel in the 
planning and conduct of such inventories. It is 
intended that the developed capability of the RIM 
section, both the procedures instituted and the 
personnel trained, will become an integral part of 
the OTA. 
2.0 SURFACE AREA OF FOREST LANDS: A PRIMARY 
INFORMATION REQUIREMENT IN NATURAL RESOURCE PLANNING 
AND POLICY 
A primary information requirement when conducting 
forest resource use and management planning is the 
total area covered by forest vegetation, and it's 
distribution within the area of interest. An 
estimate of 14,000,000 hectares of forested land has 
been put forward, but, this estimate was not based 
on a systematic mapping or estimation procedure and, 
as such, has not been incorporated in specific 
forestry policy or management decisions. The 
provision of this information was identified as one 
of the tasks to be addressed by the FLUP project 
and the RIM section, specifically. 
3.0 DETERMINING THE SURFACE AREA OF FOREST LANDS 
3.1 Selection of the basic approach 
When considering the various alternative 
procedures for determining the surface area of 
forest lands in the Republic of Niger several 
aspects are important. First of all there has been 
very little precedential application of large area 
inventories in the Sahel. Therefore, few 
results exist with which to compare one approach 
with another. A second consideration is the 
combination of the relatively low economic value of 
the resource and it's low concentrations. This 
eliminates from consideration approaches which have 
high costs per unit of area inventoried. A third is 
the appropriateness of the approach in the context 
of the capabilities of the GON forestry personnel 
being trained. The approach cannot include or 
utilize procedures which are highly complicated, 
rely heavily on the judgement and experience of the 
inventory specialists, or require equipment which is 
difficult to operate and/or maintain in conditions 
found in developing countries. Lastly, the approach 
must maximize the use of work and/or source data in 
existence and available. 
The best approach to furnishing this information 
to planning specialists is to produce a map which 
shows geographical distribution, extent and condition 
of forest lands. In arid land conditions, were the 
subject resource is in a very low density and widely 
distributed, and accessibility is a problem, a 
proven method for generating such maps is to 
interpret information from several levels of 
remotely sensed data and combine it with limited 
but highly representative, ground data. This 
approach was used in Mali (PIRT, 1982) and 
successfully produced terrain condition maps over 
the very large study area. The specific approach 
selected for application in the Nigérien situation 
is characterized by the following elements: 
- general stratification of the entire zone, 
creating units of a certain minimum size and 
homogeneity using LANDSAT satellite multispectral 
scanner (MSS) data.