t B2. Istanbul 2004 
USGS/OSU PROGRESS WITH DIGITAL CAMERA IN SITU CALIBRATION METHODS 
D. C. Merchant^*, A. Schenk?, A. Habib^, T. Yoon? 
? The Ohio State University, Department of Civil, Environmental Engineering and Geodetic Science, 2070 Neil Ave., 
Columbus, Ohio 43220, USA; merchant.2@osu.edu 
  
schenk.2@osu.edu 
? Department of Geomatics Engineering, University of Calgary, 2500 University Drive NW, Calgary, Alberta, T2N IN4, 
Canada, habib{@geomatics.ucalgary.ca 
COMMISSION I., WG2. 
KEY WORDS: Calibration. Camera, in situ, Digital, Aerial, Photogrammetry 
ABSTRACT: 
The United States Geological Survey (USGS) in cooperation with The Ohio State University (OSU) and Calgary University (CU) have 
developed procedures and software for the efficient calibration of metric quality aerial cameras; both film- and CCD-based sensors. With 
the advent of the Global Positioning System (GPS), and its efficient use to position the exposure station of the aerial camera, it became 
necessary to accurately establish camera interior orientation under operational circumstances (in situ calibration) to assure agreement of 
the photogrammetric procedure results with positional data provided by GPS. Disagreement between photogrammetric resection 
methods, based on laboratory calibration, and GPS results were consistently as large as one part in 1000 of the flight height. This paper 
describes the development of the airborne method of camera calibration, software development, and some results of accuracy 
improvements when using the in situ method of camera calibration. 
1. INTRODUCTION 
With the advent of the Global Positioning System (GPS) and 
other airborne sensors, it became necessary to revise the 
traditional concept of camera calibration. Influences on the 
camera and its spatial relationships to other sensors require that 
data used in calibration be collected under conditions closely 
approximating those expected in application of the 
photogrammetric system and its associated sensors (the in situ 
method). 
This paper presents a revised concept of calibration of aerial 
photogrammetric systems. Justification for this revised 
approach to calibration is presented by comparing 
photogrammetric results to corresponding GPS results. These 
results, in terms of positional information, should be in 
agreement if the full spatial accuracy of GPS is to be exploited. 
The US Geological Survey (USGS) sponsored development of 
appropriate software programs for use with the aerial method of 
calibration. Two programs are described for image 
measurement and calibration purposes. These programs are 
specialized to work in connection with use of aerial imagery. 
controlled by GPS. and taken over a suitably targeted control 
range. Either conventional film based or digital cameras may 
be treated for calibration. 
2. BACKGROUND 
The rapid acceptance of digital cameras range across the 
photographic industry from the low-end. 35 mm, hand-held 
camera to the special purpose. mapping camera. At the low 
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end, digital cameras offer advantages over the traditional film 
based cameras for purposes of measurement applications. 
Digital advantages in range of light sensitivity (speed) over a 
wider spectral response, and immediate access to imagery, are 
well known. For measurement applications, the digital camera 
provides a direct means of recovery of the internal orientation 
since its basic character provides a known and stable 
relationship between the lens and the captured image. As a 
consequence, there is now a growing interest in use of digital 
cameras for measurement applications, generating a need for an 
efficient and relatively inexpensive means of camera 
calibration. This need has recently been met by the USGS 
facility for camera calibration located in South Dakota. 
For the cameras intended for aerial surveying and mapping 
applications, both digital and film-based, the introduction of 
added sensors such as GPS and INS require careful 
consideration be given to a systems approach to calibration to 
assure the added sensors are fully exploited metrically. 
In recognition of this need, the United States Geological Survey 
(USGS) awarded a grant to provide and demonstrate a means 
for camera system calibration for the aerial mapping camera. 
During the course of the contract a Nikon DIX camera 
equipped with wide angle and narrow angle lenses was flown 
over a specially developed camera calibration range. Trimble 
GPS receivers controlled the imagery in the air. In addition, 
film-based photography was collected by a Zeiss LMK 15/23 
camera, also controlled by GPS receivers. Programs were 
developed for image measurement and subsequent camera 
calibration using Visual C++ software,