- 3 - 
Example of a Testfield 
For stereocameras and similar equipment a test field of steel has 
been made at the Division of Photogrammetry, Royal Institute of 
Technology, Stockholm. This testfield consists of 179 targets 
mounted on 8mm tubes, which extend between two horizontal frames 
approximately 2.40 meter apart. This steel cage is so-constructed 
and supported that it is free to move as a unit, but without internal 
deformation. The targets have a circular pattern with a small central 
cross. The size and shape of the circles fit the measuring mark of 
the comparator (Wild Stk 824) that is used for measuring the test 
photographs. The central crosses were used as targets in the 
"geodetic" measurements for determining the X-Y-Z co-ordinates of 
the points in the test field. The size of the test field is 
3.6x2.4x2.8 metres. The "geodetic" procedure was as follows. 
Three theodolite stations were used. Abase net of these stations and 
three reference points in the steel cage was measured with the 
theodolites used as collimators pointing parallel to each other in order 
to avoid eccentricities. Because of the great number of points and 
therefore the time involved, because of tripod movements, and 
because of the possible movements of the test field, the theodolite 
Wild T3 observations were made in sets of 6 to 1 0 points. The time 
required for every set was about half an hour. All recordings were 
punched directly on cards. In every set three reference base-net 
points in the cage were measured together with the 6 to 1 0 other 
points. To eliminate systematic errors of the theodolite, erect and 
inverted readings were taken immediately in succession without 
changing the focus. Every set of measurements was referred to the 
theodolite stations of the base net. The actual position of the 
instrument in a set was determined by a resection from the three 
reference points. The other readings were then referred to the 
station of the base net. The absolute scale of the coordinates was 
indirectly obtained from the end points of a two meter invar bar, 
which were measured with the same procedure. All checking, center 
ing, averaging and intersecting of new points were done by means of 
a CD 3600 computer, programmed by Ole Jacobi, Copenhagen, Den 
mark. The accuracy of the coordinates has been estimated to be 
0. 07 mm expressed as a standard error vector in space. During a 
two year period the accuracy remained the same, as far as the 
standard errors of unit weight of the test image coordinates indicate. 
Example of Statistical Analyses of Interior Orientation 
A metric camera is defined as a camera that has a known and con 
stant interior orientation. The calibrations that are made with the 
method described in this paper yield the interior orientation of that 
particular picture that is used in the calibration. This is also the 
case for almost every calibrating procedure. Before we can talk of 
the interior orientation of the camera, we must make sure that the 
calibration picture is representative of all the pictures that are