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

Symposium on Remote Sensing for Resources Development and Environmental Management / Enschede / August 1986
Determination of spectral signatures of different forest damages
from varying altitudes of multispectral scanner data
A.Kadro
Department of Photointerpretation and Remote Sensing, University of Freiburg, FR Germany
ABSTRACT: Within the soope of the project "forest damage inventory with multispectral scanner data" at the De
partment of Remote Sensing at the University of Freiburg, thematic mapper simulation data of different alti
tudes was acquired. Five test areas vhich differ in rorphology, forest types and forest damage degree
were sensed. For the investigation of the spectral signatures, reference panels were placed along the flying
strip (size ca. 200 sqm) for the determination of the global radiation. The data were obtained from three al
titudes (300, 1000, 3000 m) so that the spectral signatures could be determined in relation to the flight al
titude .
The scanner data of 300 m altitude enables the investigation of single trees. The data of higher altitudes only
permit the investigation of trees or stands because of the larger pixel size. The same test areas have been
used also for the investigation of spectral signatures of Landsat (TM) data. In this paper the results of the
investigation are presented and discussed.
1 INTRODUCTION
According to many investigations in the laboratory and
in situ measurements on healthy and damaged vegeta
tion using radiometric measurement, it has been de
termined that there are differences in the spectral
reflectance signatures of objects especially in the
visible, near and middle IR-regions of the electro
magnetic spectrum (Kadro 1981). This has sparked us
at the Department of Photogrammetry and Remote Sen
sing of the Univ. of Freiburg to carry out an investi
gation of computer determined spectral reflectance
properties of forest damages with data collected from
different altitudes above a large forest area (Kadro
1984, 1985).
For this purpose multispectral data were collected in
July 1984 and Aug.1985 from 300 m, 1000 m and 3000 m
above ground and TM data from landsat 5. The aircraft
data were collected with the Bendix 11 channel multi
spectral scanner (Table 1) modified by DFVLR/Ober
pfaffenhofen to simulate the Thematic mapper in Land
sat 5 (Table 2) .
To determine the incident radiation (global radiation),
reference panels were placed along the flying strip
(size ca. 200 sqm).
The data collected from the different altitudes have
the following ground resolution or pixel size:
Table 1. Spectral channels and wavelengths of the mo
dified Bendix multispectral scanner.
channel A nm
AÀnm
channel A nm
A A nm
2
465
50
8
720
40
3
515
50
9
815
90
4
560
40
10
1015
90
5
600
40
5 TM
1650
200
6
640
40
7 TM
2210
270
7
680
40
11
11000
6000
Table 2. Spectral channels and wavelengths of Landsat
5 TM.
channel A nm
ftAnm
channel A nm
£>Xnm
1
485
70
5
1650
200
2
560
80
6
11450
2100
3
660
60
7
2215
270
4
830
140
0,75
X
0,75
m
at
300 m altitude
2,5
X
2,5
m
at
1000 m altitude
7,5
X
7,5
m
at
3000 m altitude
30
X
30
m
at
705 km altitude (Landsat 5 TM)
It is possible to investigate the spectral signatures
of single trees frcm the data collected at 300 m al
titude, but data iron other altitudes make it possible
to investigate only a group of trees or stands. The
location of the test site is in the Black forest area
of south-west Germany and contains different exposures
and diverse types of forest stands with different de
grees of damages. The forest stands are mostly the
conifers of spruce and fir or these two mixed.
2 METHODOLOGY
The basic physical quantity characterizes the spectral
reflectance properties of the vegetation in the esti
mated spectral reflectance factor R (A) defined by
the equation (Kriebel 1978):
JL L. (j9 f ) cosa^ do- L> ()
. '4rx r Xr r, * r *r r Ar r
R (A) = ^y—
AW / cos 3 dAr L
Jar A w
where:
R(A) = spectral reflectance factor
Li = value for the reflected radiance of a natural
Ar
target
jr = zenith angle of the reflection
r = azimuth angle of the reflection
Sir = solid angle
*r,w = reflected radiance of the Lambertian reflec
tor (reference panel)
In this work the multispectral scanner was used to
collect information on the spectral radiance of the
vegetation and on the incident radiation of the re
ference panel vhich was placed along the flight strip.
The spectral reflectance factor is, for practical
purposes, estimated in this case as follows: