results were achieved according to the movement estimation
of the glacier. Note that
w= (u; v)
T
is the optical flow field, i.e.,
a function
w:
Ω
R
2
where
Ω
is the image domain, and
w
1
(x)
denotes the correspondence vectors obtained by descriptor
matching at some point
x
(Brox and Malik, 2011).
The first and second terms in Equation 1 represent the com-
mon assumption that corresponding image features (points)
should have nearly the same gray/black value and gradient.
The constraint on the gradient is considered to provide a cer-
tain level of invariance to additive changes of brightness that
(a)
(b)
Figure 3. (a) Examples for daily changes in
RGB
histograms (Red: black line; Green: dashed line; Blue: grey line). (b) Results
of
CA
processing, 231 images pairs were selected (red color points); the blue line describes the correlation value for the mean
value of the three
RGB
bands for all the
n-1
pairs.
PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSING
January 2018
37
