It may be recalled from section 1.55 that from test measurements in diapositives a limiting value of 
the standard error was found to be 2.5 ¡urn. Even though this result was obtained under conditions 
different from the tests of ballistic photographs there is good agreement, and it seems probable that the 
least possible standard error of image coordinates is of the magnitude 2 — 3 urn. 
2. THE RECONSTRUCTION OF BUNDLES OF RAYS FROM PHOTOGRAPHS 
In this section the numerical, mechanical and optical reconstruction of bundles of rays will be discussed. 
Detailed tests of instruments used for such reconstruction were made and the results are shown. The 
geometrical quality of the image (projector) coordinate measurement is of fundamental importance. 
2.1 Tests of a Stereocomparator 
Stereocomparators are basic instruments for analytical photogrammetry and for checking other 
instruments. The geometrical quality of a stereocomparator is therefore of considerable importance 
and must be checked continually. Some results of test measurements in Wild StK 824 stereocomparator 
are reported here. The instrument has been used extensively for calibrations and tests of cameras and 
photographs, etc., as reported in section 1, and of grids for tests of other instruments discussed hereafter. 
Since November 1962 the stereocomparator has been tested regularly. The glass grid nr 410 with 10 mm 
spacing has been used for the tests. The coordinates of the grid are known to a standard error of less 
than 1 micron. See reference 2.1:1. For the comparator tests and the determination of tolerances the 
principles discussed in reference 2.1:2 were applied. The results of the preliminary tests were published 
in reference 2.1:3. In table 2.1:1 the standard errors of unit weight s 0 of the grid coordinate measurement 
are shown after adjustment of discrepancies in 25 points according to the method of least squares. To 
complete the test results the regular errors d/? (lack of orthogonality of the coordinate axes) and dm x —dm y 
(affinity) are also shown. 
Table 2.1:1. Results of stereocomparator tests 
Time 
Operator 
Plate 1 
[older 
Left 
Right 
s o 
microns 
dp 
cc 
dm v -dm v 
X y 
10- 6 
s o 
microns 
dp 
cc 
dm v -dm XI 
X- y 
io- 6 
1962 
Nov. 
A1 
0.87 
+0.8 
-11.8 
0.82 
-2.7 
+ 3.8 
A2 
1.02 
+2.5 
- 8.5 
0.75 
-2.1 
+ 7.3 
A3 
1.06 
+4.3 
-11.4 
0.68 
+0.6 
- 0.7 
B1 
1.17 
+ 2.6 
- 7.2 
1.02 
-6.3 
+ 12.7 
B2 
0.81 
-1.7 
- 7.6 
0.80 
-5.7 
+ 9.1 
B3 
0.82 
-0.4 
- 7.1 
0.86 
-3.8 
+ 8.5 
Cl 
0.89 
+4.9 
- 9.6 
C2 
0.90 
-0.7 
-18.7 
C3 
0.96 
-5.2 
+ 6.8 
D1 
0.82 
-0.7 
- 9.4 
0.97 
-3.4 
- 1.3 
20. Dec. 
A1 
0.90 
+0.4 
+ 4.4 
1963 
7. Jan. 
A1 
0.88 
-2.3 
- 7.6 
21. 
A1 
1.06 
+ 3.4 
- 2.8 
4. Febr. 
A1 
0.87 
+0.2 
— 0.4 
20. 
A1 
1.16 
+ 3.4 
- 3.4 
27. March 
A1 
0.92 
-0.6 
- 7.9 
8. Apr. 
D1 
0.96 
—8.8 
- 6.8 
7. May 
D1 
1.00 
-6.8 
+ 2.0 
29. 
A1 
0.92 
+4.9 
- 5.0 
26. Aug. 
A1 
0.84 
+ 3.1 
— 0.8 
0.88 
-3.9 
+ 6.4 
5. Nov. 
M 
0.85 
-3.8 
- 0.6 
12. Dec. 
A1 
1.06 
-4.1 
-10.4 
27. 
A1 
0.89 
-4.8 
- 3.0 
1964 
11. Jan. 
A1 
0.93 
-7.2 
+ 4.4 
Averages 0.93 0.90 
27