International Archives of Photogrammetry and Remote Sensing, Vol. 32, Part 7-4-3 W6, Valladolid, Spain, 3-4 June, 1999 
127 
represented in this window. With time, the image analysts gain 
more experience in image fusion and are therefore capable of 
introducing better start values for the parameters in the process. 
Similar types of areas and datasets require similar values for a 
successful merge. Crucial in the overall achievement of image 
fusion is the adjustment of the colours in the final product. The 
same product can look very different depending on the 
histogram stretch and assignment of colour in an RGB display. 
The use of filters for noise reduction or edge enhancement is a 
sensitive matter in visual image interpretation. Depending on 
the scale and type of feature to be looked at, filters can help 
understand the image. In some cases however, it leads to a loss 
of detail which might be relevant for the application performed. 
It has to be decided on a case by case basis, if and when to 
apply filtering to VIR or SAR data. 
Further research is necessary in the development of help tools to 
support the understanding of the content of fused products 
along with quality measures. Future efforts in image fusion at 
the WEUSC will be devoted to more standardization in order to 
streamline the production of fused images for certain 
applications. Currently, many techniques and image 
combinations are used following a trial and error approach. The 
experiences of the group of image analysts are vital to the 
definition of development strategies of the data fusion system. 
ACKNOWLEDGEMENTS 
The authors kindly acknowledge the contribution of the 
WEUSC staff, in particular the image analysts, to this article. 
REFERENCES 
Cheng, P„ Toutin, T. and Pohl, C., 1995. A comparison of 
geometric models for multisource data fusion. In: Proceedings 
of Geoinformatics '95 - International Symposium on ‘RS, GIS 
& GPS in Sustainable Development & Environmental 
Monitoring’, Hong Kong, pp. 11-17. 
Gillespie, A.R., Kahle, A. B. and Walker, R.E., 1986. Colour 
enhancement of highly correlated images: I. Decorrelation and 
HSI contrast stretches. Remote Sensing of Environment, 29(20), 
pp. 209-235. 
Mouat, D.A., Mahin, G.G. and Lancaster, J., 1993. Remote 
sensing techniques in the analysis of change detection. Geocarto 
International, 2(2), pp. 39-50. 
Pohl, C., 1996. Geometric aspects of multisensor image fusion 
for topographic map updating in the humid tropics. ITC 
Publication No. 39, ISBN 90 6164 121 7, 160 p. 
Pohl, C., 1998. Tools and methods used in data fusion. In: 
Proceedings of EARSeL Symposium on 'Future Trends in 
Remote Sensing', Lyngby, Denmark, Gudmandsen, P. (Ed.), 
Rotterdam: Balkema, ISBN 90 5410933 5, pp. 391-399. 
Pohl, C., Munro, D. and van Genderen, J.L., 1997. Enhanced 
image analysis through multilevel data fusion techniques. In: 
Proceedings SPIE ‘Signal Processing, Sensor Fusion, and 
Target Recognition VI’, Orlando, Florida, USA, Vol. 3068, pp. 
32-39. 
Pohl, C. and van Genderen, J.L., 1998. Multisensor image 
fusion in remote sensing: Concepts, methods and applications. 
International Journal of Remote Sensing, 19(5), pp. 823-854. 
Prisco, G., Valero, J.L., Menu, E. and Villemaud, O., 1997. 
Multimedia and VR representations of Earth Observation (EO) 
data for operational applications. In: Proceedings of the DASIA 
'97 Conference on 'Data Systems in Aerospace', Sevilla, Spain, 
SP-409, pp. 73-78. 
Richter, R., 1997. Correction of atmospheric and topographic 
effects for high spatial resolution satellite imagery. International 
Journal of Remote Sensing, 18(5), pp. 1099-1111. 
Shettigara, V.K., 1992. A generalised component substitution 
technique for spatial enhancement of multispectral images using 
a higher resolution data set. Photogrammetric Engineering & 
Remote Sensing, 58(5), pp. 561-567. 
Singh, A., 1989. Digital change detection techniques using 
remotely-sensed data. International Journal of Remote Sensing, 
10(6), pp. 989-1003. 
Singh, A. and Harrison, A., 1985. Standardised principal 
components. International Journal of Remote Sensing, 6(6), pp. 
883-396. 
Toutin, T., 1994. Multisource data integration with an 
integrated and unified geometric modelling. In: Proceedings of 
14th EARSeL Symposium on Sensors & Environmental 
Applications, Goteborg, Sweden, pp. 163-174. 
Wald, L., 1998a. An overview of concepts in fusion of Earth 
data. In: Proceedings EARSeL Symposium on 'Future Trends in 
Remote Sensing', Lyngby, Denmark, Gudmandsen, P. (Ed.), 
Rotterdam: Balkema, ISBN 90 5410933 5, pp. 385-390. 
Wald, L., 1998b. Data fusion: A conceptual approach for an 
efficient exploitation of remote sensing images. In: Proceedings 
EARSeL Conference on 'Fusion of Earth Data’, Sophia 
Antipolis, France, Ranchin, T. and Wald, L. (Eds.), pp. 17-23.