The following results have been found:
Strip 6010a
s 0hk
- 3.36 c
S ^hk
= 2.18 c
„ 6010b
S 0 Ilk
= 2.34 c
S 0|,k
= 2.74 c
„ 6011
S 0hk
= 2.40 c
S fl.ik
= 2.04 c
All the strips
S 0 hk
= 2.87 c
S flhk
= 2.37 c
The numbers indicate the standard errors of two opposite horizons
in the horizon position because the influence of the reference value
error has been considered a systematic error. In the strip 6010a
S0 hk 2
= 2.38 and the confidence limit according to the F-distribution
sQ hk 2
on the 2.5 per cent level is 2.31. So s () is almost significantly greater
than sq ■ "The reason will be accounted for later on. The accuracy of
“hk
the horizon image coordinates can be calculated by means of the for
mula (25) after using the accuracy values instead of the precision
values. The results are as follows:
Strip 6010 a 0
„ 6010b 0
„ 6011 0
s o
0.044 mm Q
0.022 mm
0.031 mm Q
All the strips 0 0.035 mm Q
s o
0.028 mm
0.076 mm
0.026 mm
0.031 mm
The accuracy of the image coordinates is low. According to the
precision values a greater accuracy might have been expected. There
must be therefore other error sources, which are not found by a preci
sion determination. The most important error sources to be thought of
are the refraction, the elevation variations of the horizons, the vibra
tions of the airplane, the mechanical defects of the camera and the
interior orientation of the horizon camera. The influence of the eleva
tion variations of the airplane is eliminated when two opposite hori
zons are used. According to [20] the refraction causes a standard
error of 0.6 C in the horizon position from a flight height of four km.
As six points have been used in determining an inclination difference
0.6 c
the standard error of , = 0.24 c is obtained in the final outcome.
0 6
According to the estimation by means of maps the horizon has a
standard error of 100 m in the elevations which causes a mean angle
error of 3.0 1 ' in the horizon position or 1.2 C in the result. Eg. an inper-
435
