28 
Î7 feet (Î2.2 metres) respectively. The above results demonstrate that the 
horizon camera provided more accurate results than the statoscope. 
7.2.3 Accuracy of Aerial Triangulation 
To evaluate the accuracy of aerial triangulation over long 
distances using the horizon camera data, a block of 8 strips was chosen. Each 
strip was 130 kms long and comprised an average of 27 stereo models. The 
photography was flown with a Wild RC-9 camera at 1:50,000. Fig. 15 illustrates 
the actual errors in elevation observed in Strip 5 before any adjustment was 
made. They are typical of strips bridged using horizon data. From this figure 
it can be seen that errors in elevation propagate linearly. After bridging a 
length of 130 kms. (27 stereo models), the closing error is only 61 feet 
(19 metres). The closing errors in other strips were of the same order of 
magnitude. 
Adjustment of all eight strips and of the block was carried out 
utilizing vertical control only at the beginning and at the end of each strip. 
A sketch of the area showing the layout of the flight lines and location of 
ground control is shown on Fig. 19. 
To determine the residual errors in elevation after block adjustment, 
So 
known elevations of "24 points located within the block were compared with the 
elevations established photogrammetrically. The results are: 
Ah in 
feet 
Ah in 
metres 
% 
0 - 
t 5 
0 
- tl.5 
50 
t 5 - 
iio 
tl.5 
- Î3.1 
30 
iio - 
tl5 
Î3.1 
- Î4.6 
10 
Î15 - 
Î20 
+4.6 
- Î6.2 
10 
The mean square error in elevation observed on these points is m^ = t9 feet, 
or approximately -3 metres. 
7.3 Accuracy of Doppler Distance Measurements 
To evaluate the accuracy of the scale determined from Doppler 
navigator data, we compared the base distance given by Doppler with the base