FILTRATION OF AERIAL IMAGES IN SPECTRAL AND FREQUENCY DOMAIN FOR
IMPROVING THE ACCURACY OF AUTOMATIC DIGITAL AEROTRIANGULATION
Kedzierski. M.
Military University of Technology,
Kaliskiego 2, Street, 00 908 Warsaw, Poland
mkedzierski@wat.edu.pl
Commission ICWG IVIV
KEY WORDS: Photogrammetry, aerotriangulation, matching, accuracy, digital, processing, orientation
ABSTRACT:
Automatic digital aerotriangulation is one of the most essential processes in digital photogrammetry. Nowadays the images used in
aerotriangulation are not filtered.
The analysis of accuracy of digital aerotriangulation is based on the following parameters: standard deviations of alignment, RMSE
of control points and check points, the quantity of properly generated tie points and the accuracy of exterior orientation parameters.
A dimension of this defects is depended among other things on accuracy with which tie points have been generated. The fact that
conjugated pictures created according to rules of perspective projection can differ considerably bringing in geometrical distortions on
account of terrain drop, different elements of external angular orientation and lighting conditions and light reflections can distort
radiometric pictures on not changed images is very essential.
Therefore digital image matching of such images can have many weaknesses. In result of filtration it is possible to bring out the
same terrain details on adjoining images and eliminate the noises i.e. to enhance original pictures without loss of information. The
matching coefficient of filtered images will be higher than that of the original ones.
Some procedures of image filtration in spectral and frequency space allow to obtain aerotriangulation results corrected by about 2076.
The tests for this contribution have been performed on three blocks (among others block “Echallens”) with use of Bingo-F software.
Sigma naught has been obtained on the level of 3.9 um on block alignment. The possibility of using these filtration methods also in
automatic generation of DTM it its additional advantage.
1. INTRODUCTION
- errors arisen in process of images scanning,
A majority of present photogrammetic works needs still - errors in process of further elaboration of digital images.
conducting digital aerial triangulation. Searching, menstruation
and transmission of tie points on two or more images using one Ls aerial images E
of image matching methods is the base of automatic digital
punscontanenne sense ne seanennan ces ~
aerial triangulation. The use of adequate method of filtration of scanning
raw. scanned acrial images con increase preoision.of imago = 99 Sind —
matching and accuracy of automatic digital aerial triangulation. un
ne ss > as T — digital images |
Following procedures shown on Fig.l results of automatic
digital acrial triangulation may be improved by about-20%. Y
filtering
2. FILTRATION OF AERIAL IMAGES ;
spatial frequency
Scanning of aerial photographs is done usually with pixel from domain ' domain
15 to 25 um. Natural points may be used as tie points with
condition that image characterize itself adequate texture and
filtered image
contrast. Error of transfer of tie point to next. images is one of
crucial problems of automatic digital aerial triangulation and v
mostly depends on method used of image matching and on operation of
quality of aerial photographs. images association
Y
2.1. Filtration in spatial domain -
; | images result |
Filtration of scanned aerial images in object space is complex
process. Each case of necessity of using right filter may be
qualified by following: | aerial triangulation A
- kind of photographed terrain, :
- parameters uscd during aerial photography acquisition. Fig. 1. Scheme of procedure in aerial triangulation process
- atmospheric conditions during exposition, with filtration of images.
- errors on film arisen during photo-chemical process,
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