The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part Bl. Beijing 2008
a x ~ (^¡^ll^X A^lfl^Ay ^3 w i3-^z)
a y = (A i m 2l A x + ^m^Ay + A 3 m 23 A z ) + T r (5)
0 = (A l m 3l A x + A^tn^Ay + A 3 m 33 A z ) + T z
After substituting the scale factors A. multiplied by the
rotation matrix coefficients YYl iv , and the translation
components T x _ z , by the new coefficients b t , the
transformation equation can be rewritten as:
a x = b x A x + b 2 A Y + b 3 A z + b 4
ciy = b 5 A x + b 6 Ay + b 7 A z + b% (6)
where b x to b 3 and b 5 to present the rotation and scale
factors, and b 4 , b % are translation coefficients. Equation (6)
represents the mathematical form of the 3D affine LBTM.
2.3 Rectification by 3D Affine LBTM
The research in this thesis will apply this 3D affine LBTM for
high-resolution satellite imagery rectification, and then
evaluate the accuracy of the result. The basic image
rectification procedure is studied in Chapter 1, and in this
section, we will analysis rectification arithmetic using the
program language by matlab step by step, and all these
arithmetic made by Shaker, A., 2004.
Firstly, determine several ground control points for coefficients
calculation and accuracy analysis and numbers of ground
control lines for coefficients calculation. Acquire image space
2D coordinates (*., y.) on the image and object space 3D
coordinates ( < X i ,Y i ,Z i ) on the ground. It needs to get two end
point coordinates for every GCLs and calculate the length of
every line on the image and ground. But these points on the
lines need not to be conjugate points between image spaces and
object spaces.
Secondly, the parameters will be inversely calculated in the
software, the main principle of which is expressed in Equation
4.6 and the whole prudence for arithmetic 3D affine LBTM.
Then the eight-parameters will all be computed from the
transformation model and the characteristic linear features with
the method of least square in the program.
Finally, all the pixels on the image will be defined by new
coordinates by 3D affine LBTM. Achieve the image
rectification. Accuracy analysis will process by root mean
square of ground coordinates for GCPs.
3. TEST ARTIFICAL DATA
LBTM is a new kind of non-rigorous mathematics
transformation model, the stability and adaptability for
different kinds of terrain, different linear feature attitude and
distribution need to be considered first, so the date for practice
must be relative perfect, the error must in tolerance range and
can be evaluated. And the accuracy influence will be claimed
mainly come from forecasted errors and transformation model.
Due to the reasons above, artificial data is needed first for this
project.
Data sets covering a 10x10 square kilometers area were
simulated to test the developed mathematical model discussed
in this paper. Three different elevations of terrain conditions
were established for the artificial data. The first condition was
simulated for flat terrain by an elevation difference of less than
50m. The second condition was simulated for hilly terrain by
an elevation difference of about 500m. The third condition was
simulated for mountainous terrain by an elevation difference
over 1000m. Thirty well-distributed ground points were
established for every condition in the object coordinates system.
The three groups of the ground points for three conditions of
terrain were considered to have the same planimetric locations
and the only difference for them was in their elevations. The
original coordinates of the four comers are clockwise: (10km,
10km), (10km, 20km), (20km, 20km), (20km, 10km). Figure 2
shows the distribution of the ground points in plane, which is
made in autoCAD interface, while Figure 3, a b and c shows
the three different terrain shapes of the artificial data.
(10km, 20km) (20km, 20km)
(10km, 10km) (20km, 10km)
Figure 2: Distribution of the artificial ground control points in a
plane
(a)Flat terrain
(b) Hilly terrain
(c) Mountainous terrain
Figure 3: Three different terrain shapes of the artificial data
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