×

You are using an outdated browser that does not fully support the intranda viewer.
As a result, some pages may not be displayed correctly.

We recommend you use one of the following browsers:

Full text

Title
Remote sensing for resources development and environmental management
Author
Damen, M. C. J.

976
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
greater detail.
There may b
satellite, ca-t
in the order <
taining the m
ties of the
spatial resol
surface area j
in combinatioi
Thorough explo
should precede
In addition
serving specif
Tropical Eartl
studied by Inc
cations in equ
In the over 1
sing and progi
Programme of
mentioned. Dui
operation in 1
has been high]
cessful intern
together with
programme. The
tal use of mi
for applicatio
This programme
climate resea:
future operatd
this respect <
tion. After El
expected lifel
the mission wd
in 1993.
The ESA Ear
which started
dedicated to
and ice observ
With regard
tion is expec'
aperture data
me will offer
images in C-
related to re<
America and i
future land-o:
90-ties with
by means of an
operational u
monitoring of
PHOTOGRAMMETRY
Although the
ation satellit
in small-scale
vision, most
limited intere
limited spati
stereoscopic ]
able for most
however, of
making use of
libration of 1
mapping system
The situation
years with 1
stereoscopic
large format
them is even m
The question
into "imagegr
past years bee
field of pho1
with the intri
use of radar
cameras in cl<
ple. Correctic
tant when sate