ALPMON FINAL REPORT - ARC systems research

Contract ENV4-CT96-0359 ALPMON
4 Concept for the Establishment of a Remote Sensing Based Alpine
Information System
Based on the results derived within the ALPMON project and the outcome of their evaluation guidelines
could be established for a remote sensing based Alpine Information System to be introduced to the
Alpine Convention. The details for the single tasks are given in the respective work package reports.
Here, only the main aspects for the establishment of the remote sensing data base shall be described.
Satellite data: With respect to the area coverage and the related processing efforts as well as with
respect to the data costs it is recommended to use Landsat 7 TM data for a data base covering the
entire Alps (compare cost estimation, Table 16). For a coarse estimation of vegetation or forest cover
also WIFS data proved to be useful. Only for more detailed investigations of special parameters over
limited areas the use of higher resolution data (Spot 4, IKONOS) is recommended, as these increase
the costs per km 2 significantly.
Nomenclature: The nomenclature should be used as established within ALPMON (Annex 4), as this
nomenclature is hierarchical and can easily be enhanced by additional classes or sub-classes with
respect to different applications.
Ground truth: In the course of the ALPMON project detailed ground truth was collected from five test
sites distributed over the Alps and representing most of the different Alpine landscape characteristics.
Further investigations now can be based on this harmonised ground truth data, which, of course has to
be updated with respect to the acquisition of new satellite data. Nevertheless, further ground truth will
have to be collected in areas, which are not yet sufficiently represented by the five test sites. It has to
be taken into consideration that at least for every satellite flight path, which may include several
satellite scenes, representative ground truth information must be available. Especially, in the Western
part of the Alps this is not the case at the moment.
For the ground truth survey, which should follow the common nomenclature, the following methods can
be used:
� interpretation of Colour Infrared aerial photos (1:5.000 - 1:20.000)
� interpretation of Colour aerial photos (1:5.000 - 1:20.000)
� interpretation of Black/White aerial photos (1:5.000 - 1:20.000)
� field survey
� processing of existing actual forest maps (1:5.000 - 1:10.000)
� processing of existing topographic maps (1:10.000 - 1:50.000)
� processing of existing actual orthophotos
� processing of existing digital databases.
It has to be kept in mind, that representative ground truth has to be available for independent training
as well as verification reference data sets. This means, that enough samples of each parameter and
category have to be collected for both tasks. According to Congalton (1991), a minimum of 50 samples
for each vegetation or land use category is required only for the error matrix. If more than 12 categories
are classified, the minimum number of samples should be increased to 75 or 100 samples per
category. Practical considerations more often dictate the sample size selection, and a balance between
what is statistically sound and what is practically attainable must be found. Guidelines are given to
concentrate the sampling on categories of interest and increase their number of samples, whereas
reducing the number of samples taken in less important categories. Fewer samples can be taken in
categories showing little variability such as water and sampling should be increased in categories,
which are more variable. With this, a stratified random sampling is recommended, as a minimum
number of samples are selected from each strata (stratification geometrically or by land-use).
Geocoding: The investigations have proved that the quality of the geocoding results is essential for
the accuracy of results of image interpretation and classification, especially when using multi-temporal
and multi-sensoral data sets and auxiliary information. Therefore, it is strongly recommended to apply
a parametric, sensor-specific geocoding procedure, based on ground control points and a DEM. The
co-registration of images form the same area can further improve the accuracy of data overlay. Best
results within the ALPMON project could be obtained with the Remote Sensing Software Package
Graz (RSG; by Joanneum Research) implemented in Erdas Imagine, the Satellite-Ortho Module from
PCI, or the SILVICS software developed at the JRC in Ispra by N. McCormick (1997). Only if small
scale maps (1:250.000 to 1:500.000) are envisaged, the acquisition of already geocoded Landsat 7 TM
products is recommended.
JR, RSDE, ALU, LMU, Seibersdorf, WSL 92