The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part B4. Beijing 2008
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(Left Image) (Right Image)
Figure 6, Superior Results by Using Least Squares Image
Matching(The Orange Points are the Original Position of the
Character, The Red Points are the Position of the Characters
be Disposed Superiorly)
3.5 Iterative Stereo Orientation
XV XV
The corresponding coordinates ( 1 , • 71 )and( 2 , 2 )are
obtained by accurate measurement, then resolving the relative
B X ,B V ,B Z , A a x , A co, Ak
orientation elements ( y ), the
model coordinates are obtained by front intersection formula
and then the stereo model is reconstructed.
During the program from character point detection to
orientation, a series of criterion is adopted as conditions to
insure the correct of process. The criterion includes point
character value, correlation coefficient and fluctuate parallax.
Because the process following is a sequence one, the criterion
used in each phase is localization which results in the quantity
and distributing of the results can’t satisfy the requirement of
high precise orientation. The iterative strategy is adopted to
settle the localization problem, which repeat step two to four on
basis of the initial orientation. If integrated criterion is used in
processing the effect of the stereo image auto-orientation can be
improved farther.
4. DENSE IMAGE MATCHING TO AUTO-EXTRACT
DSM
“linearity factorial” . t ^ e t j me complication degree of
the web construction algorithm is “power factorial”
0(fl\ogYl) . corn pij ca tj 0n degree of search time of the
triangle cell or web vertex is “logarithm factorial”
which is the most optimized resolution for such kind of
question as query and search. The application effect refers to
Figure 7.
Figure 7, The Irregular Triangular Web Constructed by
Corresponding Character Points
4.2 Iterative Edge Character Matching under Space
Restriction Condition
The initial irregular triangular web obtained by image character
points matching is rather coarse because the infection of
adverse factors such as occlusion, noise, shadow and aberrance
etc. The space restriction condition needs to be extended and
perfected for dense image matching. In order to avoid resulting
in wrong results, the edge character matching is adopted to
obtain typical space character lines. The lines are used to
restrict the error in the DSM and improve the accuracy of DSM.
Digital surface model (DSM) is extracted by dense image
matching. The initial irregular triangular web constituted with
corresponding points gotten from the stereo orientation is used
as geometry restriction conditions. The self-adaptive window is
used in the matching course to settle the edge fuzzy in the high
resolution image matching. The selection of self-adaptive
window makes use of the classify results of multi-spectrum
images. The image in the matching window is divided into
background and thematic information to eliminate the effects of
the discrete ground surface. The final digital surface model is
the refined of the spectrum classify and the thematic
information levels such as building and vegetation are
generated. The basic technique following refers to the down
part of Figure 3.
4.1 Irregular Triangular Web Construction by
Corresponding Points
An increment style random dynamic Delaunay triangular web
construction algorithm is promoted in the paper according to
how to make use of discrete corresponding image points to
quickly construct Delaunay triangular web with optimize space
structure and how to do effective edition (such as add or delete
vertex) on the already exist web [4]. The algorithm has such
characters: adaptability, randomicity and high efficiency
dynamic edition for great capacity of data. The capability of the
algorithm is analyzed thoroughly: the space complication
degree of the data structure involved in the algorithm is
There are abundant research on edge extraction and matching.
The Canny operator is adopted in the paper to detect edges [5],
tracking the edges to extract the vector character of the edge
after burr having been wiped off. The inflexion of the edge
character can be confirmed when the grad value of the point is
greater than a threshold. After inflexion obtained, the inflexions
on the character lines can be matched with the epipolar
condition to obtain corresponding points. Creating web with
inflexions obtained to establish triangular web. Based on the
relative connection of these grids to restrict the search range in
line character matching and make edge matching quick and
exact. Character matching methods refer to reference [6].
Figure 8, Vector Edges Extraction from Stereo Image Pairs