Thë International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part B7. Beiiing 2008
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matches are always given by Model-I for all three matching
methods, and Model-IIB gives the second best matches.
Model-IV is the worst model for matching treetop point 1 and
ground point 2. The correlation coefficients also show that the
treetop point is more difficult to be matched in comparison with
the ground point. The reason may be due to the mixed texture
and complicated geometry at the treetop.
More QuickBird matching experiments (not presented in this
paper) also confirm that, due to the view angle changes of
QuickBird sensors and the changing angle between an object
and its shadow (in particular between tree shadow and tree),
high-resolution satellite imagery such as QuickBird requires a
well-defined geometric model for their image registration and
matching; in this case, Model-I seems the appropriate choice.
Incorporating a quadratic line search with GCC or LSM
matching often improves the convergence and leads to a higher
matching correlation. From both GCC and LSM line search
results, it shows a very slight improvement of matching (cross
correlation coefficient) within a few extra iterations.
The function maximisation procedures require a tolerance
which indicates when successive function values are sufficiently
similar. Tables 1-3 also list the number of iterations (maximum
is 50). This very limited comparison suggests that a tolerance
of 0.002 gives similar results to those obtained from a more
stringent convergence tolerance, in about one third of the
number of iterations.
Figure 1: Segments of Landsat scenes (path 111, row 84). Left
image: segment of the rectified TM scene for Band 3, March
1995 (map grid: AMG, pixel size: 25m). Middle image:
segment of the raw TM scene for Band 3, February 1992 (pixel
size: 30mx30m). Right image: segment of the raw MSS scene
for Band 2, January 1987 (pixel size: 57mx79m).
Figure 2: Left and right images are two segments from a raw
QuickBird stereo pair for multiple-spectral band 4, June 2003
(pixel size: approximately 3mx3m).
GCC
LSM
Point
Model
Corr. Score
Iter.
Corr. Score
Iter.
1
Model-I
0.87377
50
0.87377
11
Model-HA
0.87245
11
0.87245
11
Model-IIB
0.86975
10
0.86975
11
Model-IH
0.86961
12
0.86961
50
Model-IV
0.86844
10
0.86844
11
2
Model-I
0.89668
14
0.89669
13
Model-HA
0.89618
12
0.89618
12
Model-IIB
0.89665
16
0.89665
14
Model-III
0.89609
13
0.89609
15
Model-IV
0.89367
10
0.89367
11
3
Model-I
0.97144
11
0.97144
11
Model-IIA
0.97139
11
0.97139
11
Model-IIB
0.97034
9
0.97034
9
Model-III
0.97041
12
0.97030
8
Model-IV
0.96727
10
0.96727
10
Model-IV
0.74198
3
0.74198
2
Table 1: GCC and LSM sub-pixel matching a raw Landsat TM
image from February 1992 (centre image in Figure 1) to a
rectified and resampled TM image March 1995 (left image in
Figure 1) for three ground control points (average computing
time is 0.03 second per point).
GCC
LSM
Point
Model
Corr. Score
Iter.
Corr. Score
Iter.
1
Model-I
0.88635
20
0.88635
18
Model-IIA
0.88634
20
0.88634
18
Model-IIB
0.84573
31
0.84575
31
Model-IH
0.84558
28
0.84558
19
Model-IV
0.75940
22
0.75940
22
2
Model-I
0.84540
44
0.84540
23
Model-IIA
0.84542
21
0.84542
20
Model-IIB
0.82646
21
0.82647
23
Model-HI
0.82466
40
0.82467
29
Model-IV
0.75606
32
0.75604
31
3
Model-I
0.93416
15
0.93416
15
Model-HA
0.93360
15
0.93360
15
Model-HB
0.88439
16
0.88439
16
Model-HI
0.88151
17
0.88149
16
Model-IV
0.85979
19
0.85979
19
Table 2: GCC and LSM sub-pixel matching an original Landsat
MSS image from January 1987 (right image in Figure 1) to a
rectified and resampled TM image March 1995 (left image in
Figure 1) for three ground control points (average computing
time is 0.04 second per point).
GCC
LSM
Point
Model
Corr. Score
Iter.
Corr. Score
Iter.
1
Model-I
0.75367
9
0.75367
13
Model-HA
0.63904
50
0.63933
50
Model-HB
0.67154
7
0.67205
50
Model-III
0.58464
50
0.58461
13
Model-IV
0.48116
5
0.48116
4
2
Model-I
0.93372
22
0.92689
14
Model-HA
0.92933
50
0.92693
50
Model-HB
0.92534
50
0.92358
50
Model-HI
0.92357
50
0.92320
50
Model-IV
0.89629
4
0.89629
5
Table 3: GCC and LSM sub-pixel matching of two QuickBird
bush images for treetop point 1 and ground point 2 (average
computing time is 0.03 second per point).
6. CONCLUSION AND DISCUSSION
The correlation results from the gradient cross correlation are
nearly identical (both the matching results and iterations) to
those of the least square matching. However, the gradient cross
correlation method combines radiometric correction and
geometric correction into a single step, which makes its
parameter estimation and practical computation implementation