positioning 
roach FARA 
ica, Vol. 15, 
timmung für 
AR Global 
Geodátische 
20 
Resolution“, 
/ Kinematic 
ote Sensing, 
R. [1995]: „A 
trollers and 
ages, Leica, 
Galyean P. 
WADGPS“, 
al Technical 
Institute for 
, September 
\SCOT/GPS 
n, 6 pages, 
tic Errors in 
Ambiguity 
Archives of 
. XXIX, Part 
> Congress, 
, Wide Area 
pts for Early 
98.:94.-- 7th 
llite Division 
1, Salt Lake 
anding GPS 
hose Words 
mposium on 
matics and 
DIGITAL AERIAL TRIANGULATION 
Toni Schenk 
Department of Civil and Environmental Engineering and Geodetic Science 
The Ohio State University 
1958 Neil Avenue, Columbus, OH 43210-1247 
e-mail: aschenk@magnus.acs.ohio-state.edu 
Commission III, Working Group 2 
KEY WORDS: Digital Photogrammetry, Automation, Aerial Triangulation, Algorithms, Vision. 
ABSTRACT: 
Aerial triangulation enjoyed great success during the last 30 years. Highly efficient block adjustment methods 
are now in widespread use. À more recent development began a few years ago by integrating GPS into the aerial 
triangulation process. This will significantly change the way control information is used. GPS, together with 
advances in navigation systems and camera stabilization, highly accurate flight missions are now possible. All 
this remarkable progress will be equaled by new developments in digital photogrammetry. Several digital aerial 
triangulation systems are now in various stages of development. Two distinctly different approaches can be 
observed: interactive systems that require human operator guidance and softcopy workstations; and automatic 
systems. Automatic aerial triangulation systems attempt to reduce the aerial triangulation problem to a batch 
process, with little or no help of a human operator. Today’s systems are close to meeting this challenge, 
but the identification and measurement of control points remains an interactive task. The paper focuses 
on automatic aerial triangulation. Major effort is spent on identifying essential tasks that are independent 
of existing systems. The tasks, such as selecting suitable tie points, determining accurate approximations, 
and matching multiple images, are derived from the objectives of digital aerial triangulation considering the 
potential of image processing and computer vision. The solution of these essential tasks brings a myriad of 
challenging problems. The concluding remarks comment on the differences between traditional and digital 
approaches and discuss the consequences. 
KURZFASSUNG: 
Aerotriangulation erfuhr in den letzten 30 Jahrn einen beispielhaften Aufschwung. Leistungsfáhige Blockaus- 
gleichungs Programme sind heute im weltweiten Einsatz. Wie viele andere Disziplinen wird GPS auch die 
Aerotriangulation nachhaltig beeinflussen, z.B. durch die Art und Weise, wie Passpunkte verwendet werden. 
Die digitale Photogrammetrie wird neue Änderungen bringen. Der Übergang von analytischer zu digitaler Aero- 
triangulation wird so bedeutend sein wie seinerzeit der Wechsel von analogen zu analytischen Methoden. Heute 
kann man zwei Arten von digitaler Aerotriangulation unterscheiden: interaktiv und automatisch. Automatische 
Verfahren zielen darauf ab, den ganzen Prozess ohne Hilfe eines Operateurs abzuwickeln. Dies scheint in der Tat 
möglich zu sein, mit Ausnahme der Identifikation und Messung von signalisierten Punkten. Der Schwerpunkt 
dieses Beitrages liegt in der Ausarbeitung von fundamentalen Prozessen, die es in der automatischen Aero- 
triangulation zu lösen gilt. Zu diesen Prozessen gehören die Auswahl von geeigneten Verknüpfungspunkten, 
sowie deren Übertragung in angrenzende Bilder mit anschliessender Messung (Mehrfach-Bildzuordnung). In 
den Schlussfolgerungen werden die wichtigsten Unterschiede zwischen traditioneller und digitaler Aerotriangu- 
lation diskutiert. Aus diesen Unterschieden ergeben sich einige wichtige Konsequenzen auf die ebenfalls kurz 
eingegangen wird. 
1 INTRODUCTION 
The development of aerial triangulation during the are taking place—aerial triangulation is going digital, 
last 25 years is a major success story! Consider, a change that is as significant as the transition from 
for example, the increase in accuracy from 25 pm to analog to analytical aerial triangulation methods a 
5 pm, a tenfold increase in performance and relia- quarter of a century ago. This paper is about the 
bility, and the widespread use of efficient block ad- new transition from analytical to digital methods, its 
justment methods. Other than success, is there any- challenges and prospects to researchers in and users 
thing else worth reporting? Apart from incremen- of digital aerial triangulation methods. 
tal improvements, are there any significant changes in 
n Fig. 1 illustrates the progress in research and the 
sight? The answer is yes, for exciting developments 
development of aerial triangulation systems. The 
735 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B3. Vienna 1996