The matching point is a point which has largest
correlation coefficient
N1-1 N2-1 a CT B (1)
C(a,b)= S s (1 b)y(m,n) - I)(T(m,n) - T)
m=0 n=0 10 To
where I 1 5
= —— I(a,b)(m,n) ,
NixN2, "7 dao
T 1 NS
= T(m,n) ,
NIx N2 -0n=0
N1-1N2-1
[Cab = $ > {1(a,b)(m,n)-1}? :
m=0n=0
N1-1N2-1 ;
Tes. S «X offimn)-Tj:
m=0n=0
And the distance between the matching point of
stereo pair image is called by parallax. The
correlation analysis method can obtain height
data from the parallax PQ as shown in Fig.2.
In the correlation analysis, it is very important to
decide to the imaging angle which is represented
the Base Height Ratio (B/H) as shown in Fig.2.
The stereoscopic images (Nadir image and
Forward image) for this experiment are shown in
Fig.3. The central cross section of this terrain
model is shown in Fig.4.
These images are numerical height pattern using
à computer simulation. And they are added to
variation of the signal level (maximum 4%)
because of imitating the natural earth’s surface.
For this simulation, we investigate the
correlation window size which is important
parameter for the correlation coefficient analysis
method. Here, the correlation window size is
which cut partial image from each whole image for
the purpose of comparing to correlation coefficient,
when refer to matching points both images. The
window sizes are shown as N1X N2 size in Fig.1.
Figure 5 shows results of correlation analysis for
correlation window size. If the window size
increases, more accurate results can be obtained.
It is evident to take a large size and a square.
According to these results, we regard the size of
9X9 as the most suitable size from analysis
results and computing time. We simulate the
following examinations with 9X 9 window size.
——» M <— —— M «——
|
o | E
v] Ge b) ame | NED
l IM — \ N , v 8 - 4 \ \ \
INECCOO 4I 1] 4 8h )y)))
M NN = //] M ! $-172/]]
^ NA A e A
|
Fig.1 The principle of correlation analysis for
stereoscopic image.
Nadir imaging
Fig.2 Stereoscopic imaging
(b) Forward image
Fig.3 Stereoscopic image for the simulation.
310 International Archives of Photogrammetry and Remote Sensing. Vol. XXXII, Part 7, Budapest, 1998
Fig.5