(388)
detected only on known control points, and then only where the number of
those points is superabundant.
We now proceed ro show that in photogrammetric stereotriangulation it is
possible to detect those points in the overlap area where such distortions exist.
In review a”, f”, y” and a”, f^, y" are the corrections to the angular settings
of a pair projectors about the x, y and z axes of orientation, 0; and 4,” the
errors of the bz settings, Ab the error in bx, the by setting is zero; the elevation
errors d./ and d," of points located respectively in the planes x=0 and x=b can
be expressed as:
Z bor? 72 yz
d/ z= t A b + $^ zie b a’ pts b a d yp" oss E (y^ s y),
” Z 7 + zz 77 2 + 22 / ^ yz ’ 4
d; =p Ab or 7 b a — ZI. @ fr yp 5 (y womens. Ye
In a model (& — 1) the points that are common with the model k lie in the
plane x — b and in the model & these same points lie in the plane x — o. The
height difference A zx that a point has in passing from one model to the next can
be expressed as
AZk 7 Zky—Zk—4 7 p (à bi—A br 1) + 0, —à/ 4 b(a” + a’) 4 y (8^ —f)
if the base 4 is the same in the two models, if the errors of the settings are system-
atic, and if none of the corresponding perspective rays are distorted in the y-
direction.
The quantity
e = o," — 04 4 b (a" — a)
can be determined in obtaining the summation of b A z/z for all the points N on
the plane y —0 using common points in the overlap area of two models.
ey | Vb
ave (A bn — A b1) + Ear
9
or the same summation for all the points A and A’ where the ratios of the coor-
dinates y/z are opposite
n
Sant ten ea ME té
\Z
2 2
The systematic error of the setting f — f" — f/ can be immediately deter-
mined from the relation
n n
b b ; :
Nt À za — Z. A ZA! ) =e MR sc > A? | =H (n — 1) Y bf.
2
«
- 9
The accidental errors of setting and the y-components of the deviations of
the perspective rays which modify the warp Az a little, the theoretical values of
e and of b 6 due only to systematic errors of relative orientation if, in doing this,
one has taken the precaution to eliminate the y-deformations.
