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method in resource surveys using Landsat satellite 
images. These have proved very useful for static 
mapping of the major terrain types, large structural 
elements, etc., but the spatial resolution of 80/30 
meters is insufficient for more detailed analysis. 
Thus a step-wise "zooming-in" approach was intro 
duced starting from satellite images, e.g., at a 
scale of 1:1,000,000 through Landsat blow-ups and/or 
digital images at a scale of, e.g., 1:250,000 to 
photographic mosaics and aerial photographs in 
scales ranging from 1:100,000 - 1:10,000. Ground- 
truth gathering is a final step, but can also be 
implemented in various levels of detail such as 
rapid traversing of the whole area and detailed site 
analysis of selected, characteristic areas of limit 
ed size. 
Only for small-scale, reconnaissance mapping is 
the multiphase approach not necessary because the 
spatial resolution of Landsat data is sufficient for 
this purpose. Thus the entirely new possibility for 
direct small-scale mapping was created, avoiding the 
conventional procedures of scale reduction with 
connexed cartographic and conceptual generalization. 
This applies also to topographic mapping and the 
method has been used in particular also for updating 
of maps. An important breakthrough in the field of 
small-scale surveying and mapping thus was gener 
ated. 
THE WAY AHEAD 
Since the beginning of this year, SPOT-1 satellite 
data are available with a spatial resolution of 10 
meters (panchromatic). This means that this kind of 
satellite imagery can be used directly for detailed 
resources surveying in scales of 1:25,000-1:50,000. 
The multi-phase approach, justmentioned in the 
context of Landsat imagery, is not required and this 
method will, in likelihood, be obsolete in the near 
future. 
Satellite imagery that up to the present could be 
considered complementary to aerial photography in 
resource surveying now has become competitive! Most 
types of resource survey work can technically now be 
implemented using satellite imagery alone. Only for 
geophysical surveys and for very detailed surveys 
e.g., for engineering sites for assessment of the 
timber volume, urban studies etc., aerial photo 
graphs will remain indispensible also in the forth 
coming decades. The air photography companies thus 
are bound to lose many of their resource survey 
customers in the next decades. There is, of course, 
the matter of cost, but since the gigantic expendi 
tures for developing space technology do not have to 
be paid by the resource surveyor alone, who —in 
contrast— will be charged for the full cost (in 
cluding overhead, stand-by cost of crew/aircraft, 
etc.) by the airsurvey companies, the outcome is not 
difficult to guess: the space industry will be wise 
enough to keep their prices at a competitive level. 
Another interesting consequence of the advent of 
satellite imagery having this high spatial resol 
ution is that secrecy with even detailed topographic 
and other maps, and with aerial photographs (and any 
restriction in their free availability) is complete 
ly outdated. It will be a blessing that resource 
surveyors at last have got rid of the sometimes 
staggering and frustrating problems of getting the 
imagery and further information required to effi 
ciently perform their duties of resource inventory 
and environmental management for purposes of devel 
opment. 
One may wonder —and the question has been put 
during this symposium— whether, given the poten 
tials of existing and future satellite remote sen 
sing systems, we don't risk gathering more data than 
are actually required for specific purposes. This 
would mean getting swamped with unneccessary infor- 
formation and an undue increase of the already 
gigantic problems of data handling. 
As an example, I mention the equipment developed 
for simultaneous rnultispectral recording in 10 or 
16 spectral bands. This may be of use in a number 
of cases, but most of our rnultispectral needs are 
satisfied by recording in three or four bands only. 
Thus systems developed along these lines have a 
much greater feasibility for application in orbit 
ing resource satellites for world needs. 
It is, of course, also a matter of cost: one 
could economize and optimize by collecting only the 
amount and type of information that we need and 
want. Clear specification of users' needs therefore 
ranks high among the tasks/duties of those applying 
aerospace technology to resource studies and en 
vironmental management. I am convinced the space 
industry will listen to our voices because it is 
generally understood that the budgets required for 
further technological advances will be considerably 
more willingly allocated by the various governments 
if operational and economically sound applications 
can be found immediately or are within reach in the 
near future. 
One may object that if all aerospace and other 
data on environmental resources were stored in a 
geographical information data handling and retrie 
val system, procedures could be adjusted to accom 
modate the needs of detailed, large-scale surveying 
and the needs of more generalized information for 
medium and small-scale mapping. Consequently, we 
should gather as much information as possible. This 
concept is certainly realistic and it is our goal 
for the future. Until such sophisticated informa 
tion systems have been implemented on a world-wide 
scale, however, there is scope for several types of 
satellite observation systems operating simulta 
neously and each serving specific fields of appli 
cation. This will be the reality for several de 
cades to come. This development, by the way, il 
lustrates the great weight now put on resource 
surveying and mapping as compared to a few decades 
ago when it was common practice to make a hole in 
any more or less suitable and available aircraft 
and mount a camera in it. In many cases surveys 
even had to be based on aerial photographs made 
previously for other purposes, even if they were 
not optimally suitable because of scale, acquisi 
tion season, emulsion or up-to-dateness. 
A first type of resource satellite systems com 
prises high-resolution satellites with multispec- 
tral capacity in at least a few channels for re 
cording the reflection/emission of the Earth sur 
face and with stereoscopic capacity and/or other 
means for analysing the vertical dimension of the 
terrain configuration. The Landsat satellites were 
the forerunners in this field. In the present con 
text, it is evident, however, that a non-stereo- 
scopic system with a spatial resolution of 80 or 
even 30 meters (Landsat/TM) is no match for a 
stereoscopic system with a spatial resolution of 
10/20 meters (SPOT-1). The future will certainly 
bring further developments in this type of resource 
satellite system which will cater for thematic 
mapping in scales of 1:25,000 to 1:100,000. 
A second type of resource satellites are the 
(geostationary) low-resolution satellites. Their 
characteristics of covering very large parts of the 
globe with a very high temporal resolution render 
them suitable for very small (multimillion) scale 
monitoring and mapping. Meteorology and oceanography 
are important, but certainly not the only fields of 
application. The present systems of NOAA, GOES and 
ESA Meteosat satellites are operational and will 
remain so, unaffected by the recent launch of the 
SPOT-1 satellite. Further improvements of the sys 
tems can be expected for the future, including the 
development of zooming-in facilities for temporari 
ly depicting specific parts of the Earth surface in 
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