International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B3. Istanbul 2004
gis Jn) if d «0.1
gpd yor df o dis 02 AND Hsp) RHA
test ^od HER AND (IG, TEES
interpolation otherwise
g(x, y) =
(4)
where
g(i,, j,)= intensity value of the nearest neighbor pixel to
position (x,y) respectively
Hin, jn) = laplasian value of the nearest neighbor pixel to
position (x,y) respectively
d = distance from position (x,y) to center of nearest pixel (in
pixels)
L2 > L1 = the threshold values
interpolation = Bicubic Interpolation
Figure 2. The result of orthorectification
5. DISCUSION OF THE RESULTS
In the typical orthorectification, the intensity value of an
orthoimage pixel is a result of a interpolation of the intensity
values of a group of source image-pixels independently of the
fact they are the pixels on linear elements or the inner pixels in
a homogenous area.
The proposed orthorectification strategy includes de-nosing by
using wavelets and resampling which protects the edges. In the
described research the usefulness of wavelet transformation for
image de-noising was proved. The best result gives the soft
thresholding but the critical issue is the proper selection of
threshold value.
The proposed strategy of orthorectification gives promising
results. The visual quality of edges is almost the same both in
an orthoimage and in original image. A longer computation
time in comparison with a typical rectification strategy will be
insignificant because of quick development in computing
technology.
The strategy has been implemented in GRASS GIS
environment with applying the R statistic package, both of them
represents the Open Source Initiative.
References from Books:
Kraus, K., 1997. Photogrammetry. Fourth Edition . Dummlers
Verlag 1997.
Pitas, L, 2000. Digital Image Processing Algorithms and
Applications. A Wiley-interscience Publication.
Walker, J.S., 1999. 4 Primer on Wavelets and their Scientific
Applications. Chapman & Hall/CRC, 1999.
References from Other Literature:
Erdas Field Guide, 1999, Fifth Edition. ERDAS Inc.
References from websites:
Rangarajan, R., Venkataramanan, R., Siddharth Shah, S., 2002.
Image Denoising Using Wavelets.
http://www-
personal.engin.umich.edu/-rvenkata/551 code/Report.pdf
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