94
pointing capability which result in 1) higher
temporal coverage and 2) stereoscopic image
recording. The thermal channel of the Thematic Mapper
has a spatial resolution of 120m*120m in stead of the
30m*30m of the rest of the channels. In comparing
the Thematic Mapper and the SPOT characteristics it
may be expected in general that the Thematic Mapper
is better equiped for thematic information extraction
and SPOT is better suited for cartographic
applications because of its stereoscopic capability
and the 10m*10m resolution panchromatic recording
mode.
Table 1. Sensor characterisctics of Landsat-4 and 5
Thematic Mapper and Spot system.
Sensor:
TM
SPOT
Launch
06/1982
22/02/86
resolution(m)
30*30
10*10
20*20
spectral channels(
nm)
(MSS)
1
450-
520
500-590
2
520-
600
600-680
3
630-
690
790-890
4
760-
900
5
1550-
1750
6
2080-
2350
7
10.3-
12.5 (um)
scene coverage(km) 185*185 60*(60 to 85)
temporal 16 days period 3-5 times/26 days
resolution
3.2 Thematic Mapper geometric accuracy
Next to the characteristics of the satellite system
the accuracy of the registration of satellite imagery
to maps plays an important role. The geodetic
accuracy or scene-to-map registration accuracy is
dependent on the accuracy with which the Ground
Control Points (GCP's) can be indicated on the
imagery and on the map, the topography of the area
concerned and the algorithms used for the
registration. For favorable conditions, the rectified
TM data can meet NMAS (US cartographic standard) for
map products at scales to 1:24.000 but typical GCP
configurations and average terrain conditions will
conform to standards for 1:50.000 to 1:100.000 scale
maps (R.Welch, 1985). It is expected that in general
these accuracies will be higher in the Netherlands
because of better opportunities for GCP location and
because the error associated with relief displacement
can be neglected. Therefore it is expected that a
1:25.000 scale accuracy can be achieved.
3.3 Discussion with planners
In 1984 and 1985 DHV organized a series of meetings
with central, provincial and local authorities
occupied with the planning and management of land and
water. During these meetings an inventory was made of
the needs of satellite imagery derived information.
The meetings lead to the following conclusions:
- the detail on the high resolution satellite imagery
makes it a valuable source of many relevant informa
tion
- this information can add in a cost-effective way to
many planning and manegement applications
- the information present in the satellite imagery is
not accessible to most of the planners, because
they are not familiar with the interpretation and
techniques involved in using satellite imagery.
These conclusions formed the reason for DHV Consulting
Engineers to develop techniques to present the satellite
derived information in a more user-friendly way.
This lead to the development of the Satellite Thematic
Map concept.
4 RESULTS
4.1 Thematic content of the Thematic Mapper imagery
of the "Kromme Rijn" Area
The information content of the imagery was evaluated
by comparing the imagery with the topographic map
1:25.000 and vegetation/land use maps of the area. It
was shown that the spatial resolution of the Thematic
Mapper imagery was sufficient to discriminate between
idividual fields. This was also confirmed during a
field check. The color classes which could be discer
ned on the Thematic Mapper imagery showed a very good
resemblance to the land use classes of the topographic
map.
In general grassland,forest (coniferous, deciduous and
mixed), agricultural fields, orchards, cities, villa
ges and surfacewaters could be made from the imagery.
In addition some refinements to the legend of the topo
graphic map could be discriminate on the imagery.
A differentiation between mais and fallow land, old
and young apple orchards and management practices,
for example the clearing and cutting of forest areas
could be established. Also small linear tree-elements
with up to a sub-pixel dimension could be
distinquisted. However the possibilities for the
inventory of very small (linear) features with
Thematic Mapper imagery seems restricted and must be
evaluated for every case in detail.
4.2 Combination of satellite imagery with the
topographic map
However to actually derive a land use map from the
satellite imagery the interpretation of a especially
forest, mais and orchards was difficult.
By overlaying the satellite imagery with the
topographical map this problem could be solved and an
high accuracy interpretation became possible.
Figure 1. Satellite Thematic Map of the "Kromme
Rijn" Area: scale 1:25.000.
4.3 The
As a t
Rijn" Ar
accordin
towards
Rijn" A
check f
the last
A part o
topograp]
map showi
1984. F<
topograpl
photograj
august 2't
the map
between ]
within tl
land use
5 C0NCLUS
From the
imagery
and actua
by using
accuracy
satellite
topograph
a framewo
imagery ii
a large i
forms a f.
informatii
presentat:
For instai
of foresl
applicatic
Thematic f
a raster c
very suit
Land Infoi
combinatic
registrati
derived fr
of SPOT wi
instance i
detailed
Satellite
for prese
new gener
satellites
drasticall
planning
in the Ni
industrial:
REFERENCES
Colwell,R.i
and 2,
Sheridar
End report
research
of Remot
Dutch)
Landsat-4 S
Vol. 1-4
Lillesand,T
image in
T.R.Jord
Evaluate
cartograj
Thematic Maj
Engineer:
Spot simulal
the 1984
Corporate
