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Proceedings of the Symposium on Progress in Data Processing and Analysis

The results of the grid measurements have not been expected. In the case of the
panchromatic SPOT images only 38 % of the points could be measured. The left
panchromatic scene is from August 14, 1986, the right from June 17, 1986. From
June to August the colours in rural areas are changing - in June grain is green, in
August yellow. Caused by this, the operator was very often not able to set down
the floating mark, also automatical correlation has not been possible.
The large pixel size of 20m on the ground for the multispectral SPOT images is
causing low contrast in large fields and the operator has problems in setting down
the floating mark. But we should not neglect the not optimal base to height ratio.
By theory, which is confirmed by the differences at check points, the Z-accuracy can
be better by a factor of 3 if images with maximal inclinations are available.
The relative and absolute pointing accuracy in KFA-photos has been better than the
determination of control points. The value of +/- 15.1 m is corresponding to 7pm
x-parallax, which is not far from the pointing quality in usual aerial photos. It
seems, the results at control points are caused by the limited control point quality.
: height
1 :
22 m
1 :
11 m
table 6: accuracy of height
1 :
11 m
1 :
5 m
LFC and MC
The measurement of altitudes is depending upon the base to height relation which
can be shown at the results obtained with the LFC and the MC. The values are
corresponding to +/- 8 pm x-parallax, which is very close to the KFA. The KFA has
a unfavorable base to height relation but a larger photo scale.
5. Happing with Space Images
With images from MC, LFC, SPOT and KFA sufficiant mapping accuracies for scales
1 : 25 000 and smaller are possible. The adequate contour intervall is not sufficiant
in any case. But for large areas in the whole world the height information in the
existing maps are not so good. For example in the mountains in South America
altitude errors of 400m and more are existing. In addition for map revision only the
horizontal situation is important. More relevant is the correct identification of
The completeness of object recognition is depending upon the image resolution or
pixel size, the contrast and the spectral resolution. Caused by the large photo scale,
the KFA has the best radiometric resolution. But it is not simple to compare the
pixel size with photo resolution.
Based on edge analysis (Michaelis et at 1989) the ground resolution of panchromatic
SPOT images has been investigated (table 8). A very clear dependency to the image
contrast is existing. The relation between the 10 m pixel size and the ground
resolution is between factor 2.1 and in the extreme case 5.2. Also the photo
resolution is a function of the contrast, so a value of 2.5 is realistic.