3. Join the disconnected edges guided by th
A simple case of digitizing inner and outer e building a portion of image is shown in t
orange boundaries show the manually digiti edge of the building
. The upper and lower c
figure 3b are the annular region defi threshold; the edges shown in green are obta
operator [Canny, 1986]. The boundaries Canny operator provide better accura
digitization.
Fig. 3: a Digitized boundaries, b Ref
2.9 Matching of Edges and DSM Generat
The DSM is obtained through the matchi images at interval of four pixel units. Fig. 4
DSM. Fig. 5 shows the normalized DSM
from subtracting the derived DTM from th that the majority of the buildings can be det
DSM. It is intended to use the DSM as boundary extraction at later stage.
The positions of refined edges are known in shown in Fig. 6a, and the corresponding p
in the other image using the image to gro image transformation as shown in figure
displays matched points. The position in one image is matched aro
position of the other image. The correlation as 0.9. About 30 of the points get matc
computed for all these points which event height of the building edge. The variations
at different points of the same roof top selec of 1m. The average height of all these po
height of the object assuming roof to be a building height with respect to ground
subtracting ground height derived from DTM
Fig. 8a points on refined Fig. 8b Estim edges in nadir image on
imag 26 deg v
Figure 8c Ma edges of the im
26 deg the digitized edges.
er edges of the circular n the figure 3a. The
itized inner and outer r circles in magenta of
efined with suitable btained through Canny
ies obtained through uracy than manual
Refined boundary
ration
ching of the epipolar 4 shows the obtained
M which is obtained the DSM. It is clear
detected in normalized as cue for building
in near nadir image as g points are estimated
ground and ground to ure 6b. Figure 6c
around the estimated on threshold is chosen
atched. The height is entually represent the
ns of calculated height lected are of the order
points is assigned as a plane surface. The
und is obtained by TM.
timated points age acquired with
g view angle
Matched points on the image acquired with
eg view angle
2.10 Site Model Generation Proce
The flow chart of site model gene figure 7. The basic inputs are at le
images of the area of interest. information is available in anci
physical sensor model, the relativ estimated. The rational polynomial
terrain independent mode. The ep for these views. A dense DSM
normalized DSM and Digital Te buildings are delineated by 2-D
procedures. The points on the ed image. The remaining unmatched
and refined in 3D viewing mode. T matched edge pairs. The ground lev
the building height. The height, de Terrain model are inputs for objec
software.
Fig 7: Block diagram of site m
3. RESULTS AND
3.1 Results of Relative Orientati
Table 1 shows the results of relat images. Fourteen conjugate poin
overlapping images. Five points w residual orientation parameters.
remaining conjugate points. Startin near nadir image, the image pos
estimated in the second image. compared against the actual posit
C ar t os a t- 2 m u ltiv ie w im ag e a n d an c illar y
info rm ation S en s or m od elin g an d
g en er at io n o f r atio na l po lyn o m ial co eff ic ien ts
G e n er ation o f e pip ola r im a ge s
2- D D igit iz at io n of o utlin e o f b u ildin gs
R efin ing d igit ize d e dg es u s in g C an ny op er at o r
G e om etric a lly c on st r ain ed m a t c hin g
o f ed ge p o int 3 -D d igitiz atio n of
u nm atc he d ed ge s R e fin ing d igitiz ed e dg es
u s ing C an n y op er at o r C o m pu t ing the he igh t
of b u ild in g O b jec t M od elin g
an d vis u aliz at io n
ocess
eneration process is depicted in least two Cartosat-2 multiview
st. The attitude and position ncillary data files. Using the
tive orientation parameters are ial coefficients are computed in
epipolar images are generated SM is used for generating
Terrain Model. The edges of D digitization and refinement
edges are matched in another ed edges are manually digitized
The height is computed for the level height is subtracted to get
delineated buildings and digital ject modelling and visualization
e model generation system.
D DISCUSSION ation
lative orientation of multiview oints were identified on the
s were used for computation of s. The results are shown on
rting with the image position in position of conjugate point is
. The estimated positions are sitions, the difference between
G e ne r ation o f de ns e D S M
G en e ra tio n of n D S M a nd
D T M
XXII ISPRS Congress, 25 August – 01 September 2012, Melbourne, Australia
300
the actual and estimated position is shown direction. The achieved average value is 0.0
in line and pixel directions respectively. The is 1.392 and 0.99 in line and pixel direction r
Table 1 Results of Relative orientation of M Cartosat-2 images Washington
Actual line no
Actual pixel no
Estimated Line no
Pixel no Alo
tra 18000.6
154.037 18000.6
153.967 18164.3
509.96 18166.1
507.942 18234.6
507.42 18234.2
508.151 18216.2
875.47 18213.5
874.369 18235.6
1043.02 18234.8
1043.31 18247.2
1134.07 18248.7
1134.07 18285.1
1429.53 18285
1429.88 18528.4
1966.17 18529.6
1967.36 18518.4
2135.51 18517.7
2136.15
std dev Average
3.2 Comparison between rational poly
