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Title
International cooperation and technology transfer
Author
Mussio, Luigi

269
Resampling
For the creation of the final image, one having axes parallel to
the external reference system, the technique of inverse mapping
is used . which consists of filling an appropriately dimensioned
empty image with values obtained by interpolation of the
original image.
X? X'p
Ongsnai smage matrix Recced image matnx
fig. 5a: the inverse method of rectification
The algorithms used for the resampling work according to three
methods: nearest neighbor assignment bilinear interpolation or
bicubic splines.
m ~ | -ui*«-sisî*-suî** is 0 2Sfc?
*» * ‘Ha** is
* (Ax - 1)
A 'M~
_%•. resampling methods: bicubic spline interpolation
The formula used by the zero order interpolation (nearest
neighbor) is:
^i r \
a ?4«-T
Ax «os & ay Ax'¿OS & Ay <0.5
Ax «OS & Ay a 0,5
ax ao.s & ayac.5
fig. 5b: resampling methods: zero order interpolation
The formula used by the bilinear interpolation is:
Input image matra A
Output image matra A*
^'k,i ** A,j
* & x ( A i+ t.j * A i.j}
* ¿Y{ A i.i+i * A fc _|>
+ Ax * Ay(A{ j - - A* A i+1J *t)
fig. 5c: resampling methods: bilinear interpolation
Applications
The software has been largely used for the rectification of the
images for which two images of the survey work for the Arena
of Verona have been reported.
The formula used by me bilinear interpolation is:
fig. 6b
Figures 6: the residuals of some control points in the Arena survey