International Archives of Photogrammetry and Remote Sensing, Vol. 32, Part 7-4-3 W6, Valladolid, Spain, 3-4 June, 1999
For the fusion with AIF, a variance of 0.01 and a window size of
5x5 have been selected iteratively. The combination of the
fusion techniques, compared to each one alone, showed the best
results: edges were highlighted and spatial differences in forest
stands were smoothed.
A third fusion product for the comparison was the QuickBird
simulation. An IHS transformation was used with input the TM
band 5, 4, and 3 and the scanned aerial photograph with lm
resolution. This product was used to evaluate the potential of
high resolution satellite data, as well as for a comparison to the
BAV aerial photograph.
Table 4 shows a summary of the used image products (single
images and fusion products) as input for forest stand border
delineation in the test site Lorrach.
Image
Product
Description
Symbol
1RS-1C pan
Linear contrast stretch under forest
mask, 5 m resolution
Pan
TM 5,4,3 +
1RS-1C pan
IHS colour transformation with con
trast stretch of the panchromatic
band, 5m resolution
IHS_TM
SPOT 3,2,1
+
SPOT pan
1. AIF with variance 0.01 and
window size 5x5
2. IHS colour transformation with
contrast stretch of pan
IHS_SP
BAV
orthophoto
Scan with 254 dpi, contrast stretch
under forest mask, lm resolution
Ortho
TM 5,4,3 +
BAV
orthophoto
IHS colour transformation with
contrast stretch of the BAV
orthophoto, lm resolution
Qsim
Table 4. Used image products as input for forest stand border
delineation in the test site Lorrach.
For the Tarvisio test site, KVR and Landsat 5 TM data were
available. KVR images have a resolution of 2 m (Figure 1). The
problem of the highly different resolutions of both input datasets
was circumvented by using the sigma filter and the AIF method
(Steinnocher, 1997).
The first step was to resample both datasets to an output
resolution of 6m. The KVR data was processed with the sigma
filter algorithm and the Landsat data with a nearest neighboor
resampling. As input parameters for the sigma filter algorithm, a
filter window size of 9 x 9 pixels, an output window size of 3 x
3 pixels and a variance of 0.01 were used. Afterwards, a fusion
of the filtered KVR image and the Landsat TM 5 data was
carried out with the AIF algorithm. The input parameters for the
fusion were set to a 9 x 9 filter window and a variance of 0.01
for the first iteration. The variance was changed to 0.003 for the
following five iterations. The output resolution was the same as
the input images (6m).
To get a ground resolution of 2m, in a last step a Brovey and an
IHS transformation have been performed with input the AIF
filtered images and the original KVR data.
Fig. 1. KVR satellite image with 2m resolution.
For the AIF method, it is necessary to perform a very accurate
rectification of all the involved datasets. In the high
mountainous test site of Tarvisio it was necessary to perform an
orthorectification using the RSG software of Joanneum
Research, Graz.
2.4. Methodology of stand border delineation
For the evaluation of the information content, the actual stand
delineation was given to the test persons and they were asked to
evaluate the image data in two steps:
1. Visibility of the border in the image
The interpreter should decide, whether the inventory border
was visible in the satellite image. Three cases have been
defined:
Visible: stand border can be clearly detected in
the image
Not visible: stand border can not be detected
Partially visible: stand border can not be detected, but can
be implicitly inferred from external
geometry (e.g. forest roads etc.)
2. In the second step, in case of a visible border the
interpreters should delineate the stand borders in the
satellite data. If the border was visible, but had definitely
another geometry compared to the inventory data, the
interpreters had to digitize the geometry using the satellite
images.
2.5. Evaluation of the image products for visual stand
border delineation
The comparative evaluation is performed in two steps: (1)
measuring the visibility percentage of forest stand borders in
comparison to the official forest inventory maps and (2)
calculation of quality measure criteria.
Quality measure criteria proposed by Heipke et al. (1998) were
used. Heipke et al. proposed a buffer method for the quality