CORRELATION OF DATA FROM VARIOUS 
METHODS OF AERIAL CAMERA CALIBRATION 
Robert M. Spriggs 
Aerial mapping cameras must be accurately calibrated to determine 
the radial and tangential distortions in the lens-camera system and to 
compute the calibrated focal length of the camera if aerial maps with 
a high degree of accuracy are to result* The Air Force first used the 
field calibration range for calibrating aerial cameras; this calibration 
range was constructed at Wright-Patterson Air Force Base. Similar 
ranges were constructed later at Brookley Air Force Base (MOAMA) and 
Hill Air Force Base (OOAMA) for use of the depots in maintaining Air 
Force cameras. 
Although the calibration range is an accurate method of calibrat 
ing mapping cameras, considerable space is required for this type of 
installation and its use is often inconvenient and limited by weather 
conditions. An accurate laboratory method, therefore, would be more 
desirable. Two laboratory devices--the collimator bank and the goniometer 
--are in current use by commercial and governmental agencies for camera 
calibration. The National Bureau of Standards has used a multicollimator 
bank for a number of years, and the Fairchild Camera & Instrument Corpor 
ation uses an instrument of similar principle. In order to produce a 
collimator-type instrument of simpler design, a contract was negotiated 
several years ago with the Perkin-Elmer Corporation, and an instrument 
was built for the Aerial Reconnaissance Laboratory. In the collimator- 
type instruments (and the field range, also) the cameras are calibrated 
by reproducing special targets photographically on glass plates, measur 
ing their images on a comparator, and analyzing the results mathematically 
to produce a calibrated camera focal length and a lens distortion curve. 
The T-4 goniometer is a commercial device developed by the Wild 
Instrument Company. This instrument provides a visual method of camera 
calibration by permitting the observer to view the target against a 
graduated plate through the lens of the camera. This particular gonio 
meter measures radial distortion but cannot measure tangential distortion; 
the Wild Company has developed a later model with a filar-type eyepiece 
which can be used to measure both radial and tangential distortion. 
Although close correlation was known to exist between computations 
made on the field range and on the collimating devices, no information 
was available as to their correlation with the goniometer technique. 
A series of tests was conducted to determine this correlation. This 
report presents the results of these tests. 
This paper updates a Technical Report written by the author and 
published as WADD Technical Report 60-423, "Correlation of Data from 
Various Methods Camera Calibration", 5 March 1959, Wright Air Develop 
ment Division. 
AF-WP-O-AUG 6 4 2M