TOPOGRAPHIC MAPPING FROM SATTELITE IMAGES: HOW FEASIBLE IN DEVELOPING 
COUNTRIES ? 
Gabriel E. Ajayi” 
Institut für Photogrammetrie und Ingenieurvermessungen 
Nienburgerstr. 1 
Hannover, Germany 
ISPRS COMMISSION IV 
ABSTRACT: 
With the availability of high-resolution Landsat 
TM and SPOT images, space images are considered as 
being suitable for the production of medium scale 
topographic maps. 
This should be very useful, particularly in deve- 
loping countries, where the need for revision of 
the existing maps is very urgent. 
The usability of SPOT imagery for the map revision 
of an area in Nigeria is examined in this study. 
An assesment of the interpretability of some cul- 
tural features such as roads and settlements is 
done. Few of the problems which may make the ope- 
rational use of satellite images for mapping in 
most developing countries difficult are discussed. 
KEY WORDS: Satellite Images, Mapping, Developing Countries, Feasibilty. 
1. INTRODUCTION 
There has been the awareness in the mapping com- 
munity for some time now that images from Earth 
Observation Satellites could be useful for mapping 
activities. With the launching of the SPOT Sate- 
llite in 1986, there was the opportunity to prac- 
tically test the suitability of space images for 
the production of topographic maps. 
A great deal of work has been done in the area of 
investigation of the geometric fidelity of SPOT 
images and formulation of mathematical models for 
their geometric restitution (Konecny et al.,1987; 
Westin 1990; Jacobsen 1990). It was concluded 
that with SPOT images, coordinates determination 
could be done to an accuracy that would satisfy 
the requirements for topographic maps of 1:50,000, 
and in some cases 1:25,000. 
Since map production from space images promises to 
be cheaper and faster, it should be of interest, 
particularly to developing countries whose mapping 
needs seem impossible to meet using the conven- 
tional method of map production from aerial photo- 
graphs. 
Most of the tests carried out on the potentials of 
SPOT images for topographic mapping were carried 
out in the developed countries where conditions 
for surveying and mapping are very favourable. It 
is intended in this paper to examine if the infor- 
mation content of SPOT images is sufficient for 
updating the topographic map of an area in Nigeria, 
with emphasis on the identification of some of the 
cultural features such as roads and settlements. 
The status of mapping in all developing countries 
is not exactly the same; surveying and mapping in 
countries such as China, India and Brazil are more 
developed than in most of the countries in Africa, 
for example. However there a number of features 
common to most of the other countries; e.g lack of 
reliable, up-to-date maps, shortage of qualified 
professionals in surveying and mapping etc. The 
use of space imagery for mapping is examined 
against this general background. 
2. TEST AREAS AND MATERIALS 
Two test areas were chosen from a SPOT panchro- 
matic level 1A image acquired on 20.12.88. The 
image, supplied in digital form, was of poor qua- 
lity, having very narrow intensity range and deg- 
raded by stripes and scattered cloud. 
  
* student 
The only topographic maps available for these 
areas are the 1:50,000 maps compiled in 1962. 
The first test area, roughly 5km x 5km, encom- 
passes the southern and central parts of Agbor in 
the Delta State of Nigeria. The area is largely 
urban. It has a network of main and minor roads 
and several paths. 
The second area, measuring about 5km by lOkm, is 
rural, comprising agricultural communities. The 
vegetation varies between light and thick forest. 
Relief variation in both areas is less than 50 
meters and almost all the roads are unsurfaced 
and in disrepair. 
The test areas were selected 
image had been rectified. (See 
below) 
of the 
Processing 
after part 
Image 
   
    
  
Fig. Hal: 
Fig. 1(b): Rectified Image of Test Area 2 
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