Development of 2-D and 3-D
S, Schmid,C.. Some researchers propos information for edge extraction and lin
matching[Ok, A.O, Scholze, S.], our approa to extract and match line segments for two r
rooftops are modelled which means that sam to multiple points, thus, it is sufficient to m
edge of the building to compute height o Building boundaries are digitized, refined
nadir image. These boundaries along information analytically transferred to the
relation between geometrically uncorrecte image and ortho image is established using th
If two overlapping images are relatively disparity between two conjugate points is du
relief. Based on the geometry either the matched in original stereo pair or the other i
to form set of epi-polar images. In case of C angle about roll axis is significant; this mean
due to terrain variation will not be restricted Image matching strategy has to take into
acquisition process. The disparity map resolution is utilized to guide the matching i
cases geometric constraint is used to limit th dense DSM is generated using area based m
performed on epi-polar images, while featu matches the edges of buildings in raw as w
images using the geometric constraints. F matching techniques, normalized cross corr
similarity measure. In both the matching a size is increased dynamically. The sim
normalized cross correlation initiates with a two thresholds, termed as noise and acceptan
normalized cross correlation coefficient for t than or equal to the acceptance correlation
is checked for forward and reverse matching match point if the correlation coefficient
acceptance threshold for both the direction coefficient is less than the acceptance thresh
the noise threshold, the template size for re space is increased and correlation coeffici
The noise threshold is selected as 0.4 and a is selected as 0.9. Initial window size of the
by 13 which is increased in steps of two pix repeated for at least three different sized win
is repeated for each level of image pyram points are transferred to the next level using
interpolation for unmatched point is not do original resolution images.
2.6
Computation of Normalized DSM
A Digital Terrain Model DTM is the elev landscape which does not include above gro
other hand, a Digital Surface Model DSM with their heights above the ground as well
The man-made objects with different heigh can be detected by applying a threshold
Model. The DTM is estimated using mathem The morphological operators help in bring
terrain from the DSM. The above ground o using the DSM and morph output. T
operators, namely “opening” and “closing” The size of the window depends upon the
The normalized DSM is generated by su from the DSM. Segmentation and area
buildings of desired size. Finally the build posed use of colour
line segment stereo roach does not attempt
o reasons 1 only flat ame height is assigned
o match points on the t of the building. 2
ed and connected on g with the height
e ortho image as the ed image, epi-polar
g the sensor model. ly oriented then the
due to the topographic the set of points are
er image is re-sampled f Cartosat-2, often the
eans that the disparity ted to one dimension.
to account the image p obtained in lower
g in next step; In both t the search space. The
d matching techniques ature based matching
s well as in epi-polar . For both the image
orrelation is used as a g approachs, template
imilarity measure of a small template and
tance threshold. If the r the template is more
n threshold, the point ing. It is accepted as a
ent is more than the ons. If the correlation
eshold but higher than r reference and search
ficient is recomputed. d acceptance threshold
the search image is 13 pixels. The process is
windows. This process amid .The unmatched
ing interpolation. The done for matching of
levation model of the ground objects. On the
includes the objects ell as the topography.
ights over the terrain to Digital Surface
ematical morphology. nging the background
d objects are detected Two morphological
” are used iteratively. e size of the building.
subtracting the DTM ea filters detect the
ilding outline can be constructed using the neighbourin
definition of the building, the gr gray image is also used. The DTM
which is used as an input for co height.
Fig. 6 Derived DSM Fig