experiment to evaluate resolving power. But the statistical
processing is not efficient usage of data.
In new method, an airphoto signal, refrectance of which changes
like step function, is prepared. Now let us suppose to measure
resolving power in flying direction. The airphoto signal is
laid as its edge is slightly oblique to perpendicular to the
flying direction. In this case, we can observe the edge in var-
ious locations of pixels in many columns. And the relative
locations of the pixels in the flying direction to the edge(L;)
changes linear to the column number(i) (Fig. 2).
Li eunv/4*3 (3-1)
Here, constant ce is concern to only absolute geometric correc-
tion, and it is not important for our purpose. So if the air-
photo signal is observed and the constant d is determined, it
means that essential data to calculate PSF are obtained.
A. CCT-Column eurve
{ha 15" conventient to plot COT count Lo tolumn number P i'of
pixeles included in a line near the edge (Fig. 3). Lets us call
it CC curve(CCT-Column curve). Because the edge/íisostraight,
and because the image has little distortion in small area even
if no geometric correction, observed image of line 1 is similar
toione of line 1+, and OO'curves' ofthe line 1l and l1-*1 have
sinilar figuress Indother words, if the CC: cumye of the line}
is transferred in colunmn'directiony iit overlaps to 'oneol the
line 1+1. Using this fact, we can determine the constant d.
du=s b/n (4-1)
Here, b is pixel size in line direction, n is number of columns
to transfer in CC curve(real number).
5. Calculation algorithm
Now, CC curve can be thought usual edge observation data, x
axis of which is spsece coordinate In tangent to the edge, y
axisc ofiwvhich ds 'CCT2count,” supposing ons column equal to
length d (=b/n). So, standard algorithm to calculate PSF from
edge observation data can be applied. Radiance(R(x), relative
vale) of airphoto signal is
C. Rb ( KB.) b
EE br IR (5719
Here, x : space coordinate in tangent to the edge.
the edge isycorresponding to x = OQ.
hwr: Radiance of black part of the airphoto signal.
Rb:r Radiance of white part of. the airphoto signal.
CCT count of observed image(I(x)) is expressed as following.
I(x) = fase R(x) * PSF(x-x!). dx! (5-2)
2 1% % Vis Th) Jol pom dx! (5.3)
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