In: Wagner W., Szekely, B. (eds.): ISPRS TC VII Symposium - 100 Years ISPRS, Vienna, Austria, July 5-7, 2010, IAPRS, Vol. XXXVIII, Part 7B 
400 
3.2 Analysis 
The results of the two calibration procedures indicate that the 
parameters are close to being identical (Table 2). The charts in 
Fig. 7 also show the same phenomena. However, in our 
experiments, we found that the results start varying if the 
camera is positioned too close to the targets. This observation 
seems consistent with previously reported studies on close 
range photogrammetric camera calibration (Brown, 1971). 
However, more analysis needs to be done for anything 
conclusive. Since the Box as a calibration target is meant for 
small format short focal length cameras, the distance between 
the targets and the cameras should be close enough so that 
Australis software is able to recognize the targets. The size of 
the targets, therefore, needs to be selected accordingly. 
4. CONCLUSIONS 
In this research, two methods of camera calibration that are used 
at the USGS EROS at Sioux Falls, South Dakota, USA were 
presented. The camera calibration lab is housed primarily to 
calibrate medium format digital cameras, with a focal length 
range between 20-120mm. The main calibration method uses 
the principles of self calibration and bundle adjustment on 
coded targets located on an aluminium cage. A second method 
to perform calibration was presented. This method used a scaled 
down version of the coded targets pasted on a small rigid box. 
Both the methods involve taking images of the targets from 
different camera locations and orientations. The solution to the 
bundle adjustment problem is obtained using the software 
Australis. It was shown that the solutions camera calibration 
parameters obtained from both the methods are close to each 
other. The same time the approach using the box yields 
promising results and can be used for verification of the 
calibration parameters. Further research on the box by adding 
more targets may yield results closer to the results obtained 
from the cage. There has been an increasing interest in 
calibrating longer focal length cameras (> 150mm) using self 
calibration methods. The problem becomes non trivial given the 
limitations of space. Further research is being conducted at the 
USGS on expanding the range of cameras, with regards to the 
focal length, that can be calibrated in the lab. 
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DISCLAIMER 
Any use of trade, product, or firm names is for descriptive 
purposes only and does not imply endorsement by the U.S. 
Government. 
ACKNOWLEDGEMENTS 
Sam Johnson and Alonso Holmes performed most of the camera 
calibration experiments