or the 
is dia- 
raphy 
collec- 
Isions, 
| used. 
visible 
; Were 
obser- 
liffer- 
meras 
2 tests 
verage 
from 
main 
ments 
phy of 
er, 
—— X 
oblique 
— 
Ho 
rraphy 
square 
ocated 
  
in the corners of a perspective grid, the dimensions and shape of which 
have to be computed from the image coordinates with the aid of pro- 
jective relations. Assuming the inclination angle e of the camera axis 
see Fig. 11 we have the following well known relations between the 
coordinates x'y' of the image plane and the coordinates x, y of the 
ground plane: 
h(x'cos e -- c sin e) 
  
x OTRO en) (50) 
— x'sin e + c cos e 
hy’ 
y= —— (51) 
— X’sin ¢ + c cos e 
or 
c(X cos e — h sin 
eut Ks B sin vy (52) 
X sin e + h cos ¢ 
CV 
V. mucius M nucum (83) 
X sin ¢ + h cos ¢ 
The origin of the coordinate system x, y is the nadir point N on the 
ground. 
From the given image coordinates x’y’ and the data h, c and ¢ the 
coordinates x and y were computed, staked out on the ground, and 
marked. The coordinate determination of the points on the ground was 
performed with similar methods as the points for vertical photography. 
The ground coordinates are demonstrated in Table 2. 
After signalling the points the photographs were taken under well 
defined conditions. 
The image coordinates were measured in comparators and in the 
autograph A7 and were compared with the corresponding transformed 
ground coordinates, which first were recomputed into a horizontal plane 
on the ground. The discrepancies between the two sets of image coor- 
dinates were assumed to be caused by the errors of the elements of the 
interior and exterior orientation of the camera, systematic disturbances 
in the central projection and the errors of the measurements. 
4.32 The computations 
The transformed ground coordinates in the image plane are denoted 
x", y’, and the corresponding measured image coordinates x o nt 
The errors of the measured image coordinates are defined as 
dx'— x! — x 
" 5 (54) 
= mn T9 9 
45