177
Table II.
Zeiss
L
R
0,39
0,45
De Koningh
L
nr 3975
R
De Koningh
L
0,l6
nr 3985
R
Instrument
in
cgr
syst. graduation error
m2
max.
min.
0,42
0,21
0,46
0,60
0,32
0,14
0,23
0,2I
0,15
0,07
0,l8
0,14
0,21
0,12
0,20
0,23
0,14
0,22
0,20
0,18
0,17
the Zeiss-triangulator this influence is rather important and it is
clear that in cases where the utmost accuracy is wanted, the gradua
tion-errors cannot be neglected.
A considerable improvement has been obtained for the Zeiss in
strument by rearranging the relative place of both verniers and by
fixing them so that they include an angle of approximately 100 grades.
In this case the resulting error in a measured direction is:
x T (X<P 9^ ~f" to° 9^ 4~ 200 x V 300)
•wherein
Xy ax sin© by coscp a2 sin 2<p b2 cos 2 cp
a3 sin 3? b3 cos 39 -f
xv+10o «1 coscp by sin cp a2 sin 2 cp b2 cos 2 cp
rt3 cos 3 cp b3 sin 3 cp
xv +SOO «1 sin cp by coscp a2 sin 2 cp b2 cos 2 cp
a3 sin 3 cp b3 cos 3 cp
xy +3oo «1 coscp by sin<p a2 sin 2cp b2 cos 2cp
-f- a3 cos 3 cp b3 sin 3 4>
{xy X cp +100 X cp Jf. 20o x cp 4. 300) 4 [a4 s'n 4 <p
b4 cos 4 cp
so that x ai sin 4 cp b4 cos 4 cp
The influence of the functions of 4 cp is far less than that of the
other one's so that this arrangement is obviously an improvement.
The computation has shown that the maximum and minimum value
of in this case are resp. 12 and 12 dmgr, so that after this
arrangement the differences between my and m2 may, for the Zeiss
triangulator, also be neglected.
Comparing the resulting accuracy of ca 0,20 cgr with the accuracy
of the adjustment of the measuring-mark to a point on the photograph,
which is highly dependent from the quality of this photograph and
from a lot of other factors, it is easily shown that it will be amply
sufficient.
12
