Full text: Remote sensing for resources development and environmental management (Volume 1)

Symposium on Remote Sensing for Resources Development and Environmental Management / Enschede / August 1986 
Digital classification of forested areas using simulated TM- 
and SPOT- and Landsat 5/TM-data 
Dept. Luftbildmessung und Fernerkundung, Institute for Forest Economy and Inventory, University of Freiburg, FR Germany 
DFVLR (Deutsche Forschungs- und Versuchsanstalt für Luft- und Raumfahrt), FR Germany 
ABSTRACT: In the following piece of research both SPOT- and TM-images, as well as true Landsat 5/TM data have 
been digitally classified. The results show information about the possibilities of recognizing different types 
and age classes of trees, together with a high resolution of the classified forest units. Using both TM- and 
SPOT-data it is possible to differentiate between at least three age classes in forest stands. As well as 
distinguishing betv^en coniferous and deciduos trees, it is possible to recognize certain tree types in pure 
crop stands within these classes, depending on the time of year. The correctly classified forest unit is 
influenced by the form and size of the stands, but generally stands larger than an hectare can be recognized. 
Ihe classification of the Landsat 5/TM scenes was improved by taking into account topographical information 
and by using rnultitemporal data. 
The results of the TM-simulation carried out by Kirch- 
hof, W. , Mauser, W. and Stibig, H.-J. , were pub 
lished in the research report FB-85-49 of the DFVLR 
(Deutsche Forschungs- und Versuchsanstalt fiir Luft- 
und Raumfahrt). 
The digital classification of Landsat/MSS-images has 
already been carried out in countries with extensive 
forest areas, producing good results. Offering a high 
level of efficiency, their use has been shown for ge 
neral classifications, for example seperating deci 
duos from coniferous forest for the purpose of stra 
tification. for detailed inventory methods. However 
owing to the limitations of the geometrical resolu 
tion, Landsat/MSS data have proved of little use for 
forestry classification in Centra], Europe. 
The size of the planning units in the intensively 
managed forests is usually between 3 and 5 hectares 
and the treatment units are often smaller. Whereas an 
area of 2,56 hectares is necessary for one pure 
Landsat/MSS pixel. New sattelite images from SPOT- 
and Landsat 5/TM with a high geometrical resolution 
open up possibilities for the use of remote sensing 
for forestry purpose in Central Europe. 
The strip overflown for the SPOT- and TM-simulation 
is situated west of Freiburg. Apart from agricultural 
and built up areas, the test area contains typical 
mixed deciduos forest of the Rhine valley. The main 
tree types are oak, ash and maple. There are also 
some single pure crop stands of spruce, douglas firs 
and red oak. 
A test area to the north-west of Freiburg in the 
Kaiserstuhl was chosen for the multitemporal evalua 
tion of the Landsat 5/TM data. 
This area consisted of two types of forest: 
1. "Auwald": deciduos lowland forests near the 
Rhine. The main tree types are oak, white beech, 
poplar and maple as well as pure crop stands of 
douglas firs and pine. 
2. Colline to submontane mixed deciduos forest 
consisting mainly of beech, white beech and oak, 
varying in height from 200 to 550 metres. 
The simulation of the SPOT and TM data was carried 
out on behalf of the research centre of the European 
community (IRC) in ISPRA. The SPOT-simulation took 
place on the 26.5.1982 and was performed using a 
10 band Daedelus scanner from a height of 7000 metres 
by the NGI (National Geographical Institute). The 
radiometrical simulation of the SPOT-simulation bands 
(S.S.) from the Daedelus bands was carried out by 
the CNES (Centre National d'Etude Spatial) (Tab. 1). 
The TM-simulation was flown on the 21.7.83 fron a 
height of 4000 metres by the DFVLR, using two Bendix- 
M2S-Scanners, one of which was modified to work in 
the middle infrared wavelengths. For the evaluation 
of the data, the scanner bands (T.M.S.) which most 
closely approach the TM bands were used (Tab. 1). 
The selected Landsat 5/TM-images are the scenes 
195/27 taken on the 18.4.84 and the 7.7.84. 
In order to include the different tree types and age 
classes, the test areas were selected by using ground 
truth inventories, the interpretation of infrared 
false cölour composites and the .information from fo 
rest management plans. 
The geometrical rectification of the scenes took 
place with pass points on Gauß-Krüger coordinates 
using an exponential transformation polynom. 
The signature analysis of the test areas was per 
formed by comparing histogramms, the reflection 
curves of the mean values and the presentation of 
the object classes in two dimensional feature space. 
The quality of the training areas for the simulation 
data used for the maximum likehood method was esti 
mated using a confusing-matrix. 
The sub-scenes were finally classified according to 
the maximum likehood method. For the TM-scene of 
April a more simple classification by the defini 
tion of thresholds was sufficient for a forestry 
stratification, owing to the more distinct reflec 
tion differences. For that purpose the maxima and 
minima values for all the bands were cited. 
Additional information in the form of a digital 
terrain model was used for a further stratification 
according to height. To test the accuracy of the 
classification the results were compared with forestry 
planning maps of selected areas. 
The image processing systems FIPS (Freiburg's Image 
Processing System) of the dept. Luftbildmessung und 
Fernerkundung and DIBIAS of the DFZLR were used for 
the digital image analysis.

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