facilitate the interpretation. Image enhancement and 
classification are techniques applied to facilitate the extraction 
of information by the interpreter, who is to be considered as a 
qualified professional in his own field. 
That professional field has usually to do with observing the 
earth's surface, or some aspect of it, and he will be after 
information with a spatial component: geo-based information 
A bit more specific: the interpreter must be capable in his own 
field of knowledge, and have enough professional level of 
reference to serve him in the interpretation of remotely sensed 
data for (geo-based) information extraction. 
These fields of knowledge can be categorized as the 
earth-observing sciences in the widest sense. Examples: 
Geography, geology, geomorphology, vegetation mapping, 
forest survey, land use survey, water resources survey .... 
* Metric Information 
is extracted in a different way from the data: exact positioning 
and elevation information can be extracted from modern remote 
sensing data by cartographers, photogrammetrists, geodesists. 
The purpose : mapmaking in the sense of topographic and 
contour maps. Much of this information was and still is 
extracted from aerial photography. 
With the availability of the Thematic Mapper, SPOT, IRS 1-C 
and ID, ERS, JERS, Radarsat, it becomes possible to extract 
useful spatial information in this context from satellite remote 
sensing data. Especially important in this context: the new 
possibilities for rapid and accurate map updating. 
Metric information based on remotely sensed data serves 
mapping and mapmaking in the widest sense. 
Professionals involved here include surveyors, cartographers, 
photogrammetrists. 
3. USERS IDENTIFICATION 
* The use of this information 
is not in all cases restricted to the interpreter or mapmaker. 
Planning and decisionmaking at the local, regional and national 
level, ideally should be based on solid information relevant to 
the.(development) issues at hand. 
Decisionmaking is a complex affair and not really under 
discussion here. 
Still some points should be clear: 
Decisionmaking has two phases: a technical phase and a 
political phase. 
Technical decisions usually are taken on the basis of 
information supplied, but within the constraints of the political 
decision-frame. 
Political decisions are mostly not taken on basis of 
information supplied from the data collection through the 
planning level, but on political and/or economical 
considerations. 
Such decisions are often taken a priori, leaving the planning 
level with the task of implementing them. 
Satellite remote sensing is an extremely powerful tool for the 
set-up and updating of data-bases from which such 
geo-information can be extracted. 
This identifies planners and decisionmakers at the local, 
regional and national levels as potentially important end 
users. 
There is usually an underlying echelon of officials that feeds 
them with information on which action can be based. 
This level, of (senior) technical advisers, departmental 
directors, even policy advisers, is in fact a more important 
target group for education in remote sensing utilization. It is the 
departmental top echelon, which is not directly affected by 
political change. 
This category has the imago of busy officials (bureaucrats?), 
and may not be expected to extract information themselves, but 
act on aggregated information presented to them by the level of 
technical experts and professionals in the respective fields. 
A function of the top echelon is to link the information 
available, to development objectives which may be technical 
or political of origin. This is a most complex affair, and this 
problem is by no means solved, although it has been recognized 
for many years. 
A task thus becomes, to educate planners and their senior 
advisers not only to apply remote sensing data and derived 
information, but also to identify their information requirements 
in relation to the technical or development questions that 
confront them. 
These questions often revolve around resources inventories, 
assessment and evaluation, optimization in resource utilization, 
infrastructure, environmental considerations etc. As technology 
progresses, additional questions may be addressed, such as the 
monitoring of processes and activities (natural or man-made). 
A combination of remote sensing observation techniques may 
lead to a capability for natural hazard forecasting and warning, 
later even to the monitoring of events and coordination of relief 
operations. 
4. DOMAINS OF APPLICATION 
The environment, environmental protection and environmental 
management, are gaining increased prominence as subjects of 
concern with reference to the effect of the use of resources and 
pollution. 
Natural hazards, underlying causes for natural disasters, 
likewise become more evident as causes of concern. Here, too, 
planners and decisionmakers play a decisive role in how the 
problems are confronted (or not), and remote sensing is a 
powerful tool to provide them with a database on which to base 
their decisions. 
Geo-information systems of various kinds are under rapid 
development to take their role as supports of decisionmaking in