Symposium on Remote Sensing for Resources Development and Environmental Management/Enschede/August 1986 
© 1987Balkema, Rotterdam. ISBN 90 6191 674 7 
1057 
Working Group 3: Spectral signatures of objects 
N.J.J.Bunnik 
Liaison 
The field of interest of Working Group III deals 
with research into methods for the extraction of 
object properties from remotely sensed data. 
These data can be acquired by multispectral, ther 
mal infrared and microwave sensors. The extraction 
process is based on the use of deterministic or phy 
sical models and object property estimators. Besides 
the use of (spectral) data as input, also other 
(non-spectral) object data are required for a quan 
titative assessment of object properties. 
At the symposium only papers dealing with multi 
spectral or thermal infrared data have been presen 
ted during the 6 sessions of Working Group III. 
Those papers on microwave remote sensing have been 
presented during the sessions of Working Group II. 
The total number of expected presentations for 
Working Group III was 29. During the symposium 25 
papers were presented. 
The presentations could be subdivided into the 
following three categories: 
1. Development and use of interaction models. 
2. Development of methodologies for: 
- data interpretation 
- experimental measurements 
3. Research on new remote sensing methods. 
The conclusions and recommendations with respect to 
the work presented within these categories can be 
summarized as follows. 
1.1 Two types of models have been presented: 
- descriptive models used to study radiation inter 
action processes as a function of changing vegeta 
tion and soil parameters and for special observation 
conditions like the hot-spot. 
- simple models required for practical applications 
in agriculture. 
1.2 It was recommended to develop assimilation tech 
niques based on the use of remote sensing models, 
crop growth models and field observations for the 
purpose of production estimation. 
1.3 For practical applications in crop growth and 
crop condition monitoring, simplified interaction 
models should be further developed in order to vali 
date the estimation of significant crop parameters 
from spectral data (development stage, soil cover, 
leaf area index). 
2.1 With regard to development of methodologies for 
data interpretation further work has been presented 
on multispectral and multitemporal classification, 
atmospheric corrections, feature analysis and the 
combined use of geographical and spectral informa 
tion. 
2.2 Well documented experiments have been reported 
within two different objectives: 
- to improve the understanding of different radia 
tion interaction mechanisms 
- to develop methods for the assessment of different 
factors related with crop vitality. 
2.3 Simplified methods were presented for low cost 
spectral measurements by means of (calibrated) pho 
tography from ultralight aircraft and ground level 
(only valid for a limited area). 
2.4 In the near future a workshop should be held on 
radiometric measurements with a review of existing 
methods, on standardization and on training of users. 
2.5 More attention should be paid to the statistical 
significance of ground measurements related to data 
collected by sampling. 
3.1 New results have been presented on the potential 
of hot spot measurements for the characterisation of 
vegetation. The use of a laser system has been 
demonstrated to determine vegetation density and 
height profiles. 
3.2 Within the scope of Working Group III it should 
be investigated further to which extent active 
measurements in the optical part of the spectrum can 
add new capabilities for the extraction of object 
properties.