International Archive
coordinates (Xi V, ) of other control points on the chip
can be obtained. The difference between image point
measured coordinate (xdi) and their ideal coordinates
(x; V.) is the total of all system errors caused by
imaging. Proved by several experiments, the distribution
regularity of the systematic error including its value and
direction, is in accordance with the distribution regularity of
optical radial distortion.
The surface degree of CCD chips may maintain at the level
of +1 iM . The object space plane control network is
produced on the AVIO TAB plotting table by Leica
Company, Swiss. Aided by the computer plotting functions,
a 1.1mx0.9m control grid is created on the 0.1mm thick
polystyrene film. The interval of the grid is Sem. There are
399 black solid round symbols with a diameter of 15mm on
the intersection of grids. Thus, the network might have
enough intensity, as Figure 1 shows. With regards to
experiences, the central error of each symbol is no more
than +0.05mm. With the similar method, similar plane
control networks can be created on the 8mm thick adhesive
backing glass.
Fig.1 X 2D control field
The Nikon E2 (1280x1000 pixels, sizel0 £71 ) and Kodak
DCS 4800 (2160x1440 pixels) digital cameras are used as
the test camera to implement “vertical photography” for the
control network. Select four points that are close to the
s of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B5. Istanbul 2004
image edge as the control points. Establish the projection
relationship between the oblique image and plane control
network and work out the coefficients 1.
Set the measured coordinates of symbols as (x, 2 ). The
ideal coordinates would be (xi, vj) aided by factor I.
Their difference (Ax, j Ay,) is caused by various optical
distortion errors (Ax; ’ Ay, ).
AUG mx jc
=a (6)
Av: y: Yu
Where (x.y ;) is the theoretical value, while
(Ax,, Ay;) is the distortion error.
Presented method does not touch any relationship between
the physical factors of the error. The physical factors include
radial distortion and decentring distortion in objective-lens
optics, radial distortion coefficients changing with the
focuses, radial distortion change of the object point that is
not on the focus, and other geometric imaging errors caused
by electronic and optical factors, and etc. Take the test done
with Kodak DCS 4800 as an example. Rectified according
to four corner angle points (001,015,136,150), the image
point distortion error Ar. of each control point is shown as
Figure 3. Its size and direction is in accordance with the
general deduction of distortion error of radial distortion. The
error vector directs to the center of the image frame (it
should directs to PPA: Principal point of autocollimation).
Moreover, it is easy to analyze that the distortion of the
whole image presents as from the image edge to the center,
when the distortion of the four corner points is not zero.
A primary model of distortion error Ar can be created
with these data, as Figure 4 shows. The model is created by
the distortion error Ar of the 150 points on the digital
camera chip. The unit of each direction (x, y, Ar ) is pixel.
The primary model on direction x is shown as Figure 3.
while the model on direction y is shown as Figure 6.