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,