The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part Bl. Beijing 2008
affected, apart from the noise, by the natural image texture.
Hence, the shape of the histogram of wavelet details is not
always correlated with the noise level.
Based on the studies, it has been proven that the analysis of the
equation of preservation of image relative variance is a good
indication of the noise level. The low noise level is proven by a
stable increase of the details variance along with the level of
decomposition. In case of fine-grained image texture, such
increase is undisturbed.
Great difference in the contents of random noise has been
confirmed by the comparison of images from the digital and
analogue cameras. The DMC images contain several times less
random noise than those from an analogue camera.
The studies described are not exhaustive as regards the use of
wavelets for valorisation of radiometric quality of
photogrammetric images. Since higher quality of 8-bit DMC
images generated from the panchromatic and 3 multi-spectral
components has been proven, the quality of individual
components would have to be verified. It appears that the
wavelet transform can also be used for the optimisation of tonal
mapping which takes place while transforming the signal of a
broad dynamic range of a digital camera into the 8-bit range.
In the current stage of research it is not possible to use the
results of the wavelet-components analysis as an absolute
measure of the noise content. Defining such a measure requires
carrying out a series of experiments, in which the images taken
in the different conditions and seasons, will be studied. Such
researches should be carried out in the future, because
unsatisfactory quality of the radiometric images makes
automation of the photogrammetric technology difficult and
reduces the interpretation value of the images, including
orthophoto-maps, so popular nowadays.
ACKNOWLEDGEMENTS
The investigation has been made within the scope of research
project AGH 11.11.150.949/08.
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