PHODIS AT - An Automated System for Aerotriangulation
Josef Braun, Liang Tang and Rasmus Debitsch
Carl Zeiss, D-73446 Oberkochen, Germany
Commission II, WG II/5
KEY WORDS: Surveying, Automation, Triangulation, Aerial, Digital, Automatic Aerotriangulation
ABSTRACT
Aerotriangulation is an essential task in photogrammetry. The most laboured and time-consuming work in an analytical aerotrian-
gulation is still the block preparation and measurement of tie and control points. To meet the needs from the photogrammetric
practice, an automated system for aerotriangulation was developed. The system is called PHODIS AT and is a new member of the
digital photogrammetric image processing system PHODIS from Carl Zeiss. The system is composed of the block preparation, the
fully automatic tie point determination, the semiautomatic control point measurement and the interface to diverse block adjustment
programs. The key feature of the system is the fully automatic determination of tie points in images of a block. Components of
PHODIS AT are described in this paper. First results achieved by processing various blocks from the photogrammetric practice are
presented and evaluated. It could be shown that the aerotriangulation conducted by PHODIS AT can reach the same level of accu-
racy as that of the analytical one and is even much more economic for the practice.
KURZFASSUNG
Die Aerotriangulation ist eine essentielle Aufgabe der Photogrammetrie. Die Blockvorbereitung und Punktmessung ist bis heute
die mühevollste und zeitaufwendigste Arbeit in der analytisch durchgeführten Aerotriangulation. Um den Anforderungen der pho-
togrammetrischen Praxis gerecht zu werden, wurde ein automatisches System für die Aerotriangulation entwickelt. Das System
hei&t PHODIS AT und ist Teil des digitalen photogrammetrischen Bildverarbeitungssystems PHODIS von Carl Zeiss. Das System
unterstützt die Blockvorbereitung, die vollautomatische Verknüpfungspunktmessung, die semiautomatische PaBpunktmessung und
verfügt über eine Schnittstelle zum AnschluB unterschiedlicher Blockausgleichungsprogramme. Der Kern des Systems ist jedoch
die vollautomatische Messung von Verkniipfungspunkten in Bildern eines Blockes. Im vorliegenden Beitrag werden die Kompo-
nenten von PHODIS AT beschrieben. Die ersten Ergebnisse, die durch die Bearbeitung verschiedener Blöcke aus der photogram-
metrischen Praxis erzielt wurden, werden vorgestellt und beurteilt. Es zeigt sich, daß die Aerotriangulation mit PHODIS AT das-
selbe Genauigkeitsniveau erreichen kann wie die analytische Aerotriangulation, aber viel wirtschaftlicher für die Praxis wird.
1 Introduction
Aerotriangulation is an essential task in photogrammetry.
Digital photogrammetry is characterized by the high automa-
tion of individual processing procedures and brings much more
economy to the photogrammetric practice. Digital terrain
models, for instance, can be generated automatically from
digital or digitized aerial images and so can digital orthoimages
thereafter. Using digital techniques, aerotriangulation can also
be automated now in order to meet the needs from the practice.
Since early nineties, research and development of algorithms
for automating aerotriangulation have been conducted at sev-
eral institutions (eg. Tsingas, 1992; Schenk/Toth, 1993;
Tang/Heipke, 1993; Ackermann/Tsingas, 1994; Toth/Krupnik,
1994) and now a stage has been reached for practical realiza-
tion (eg. Ackermann, 1995; Krzystek et al., 1995; Mayr, 1995;
Schenk, 1995; Tsingas, 1995).
PHODIS AT is a system that affords fully automatic tie point
determination and semiautomatic measurement of control
points for aerotriangulation. The high degree of automation
offered by PHODIS AT simplifies and accelerates block prepa-
ration and post-processing considerably. Errors that occur in
classical aerotriangulation due to misinterpretations or wrong
entries are virtually excluded with PHODIS AT by means of its
automated procedures and program checks.
PHODIS AT is a new member of the digital photogrammetric
image processing system PHODIS from Carl Zeiss. A complete
digital photogrammetric production chain can be established by
PHODIS members (cf. Table 1). Using the chain, the whole
photogrammetric production can be conducted in a very eco-
nomic way as mentioned before and, on the other hand, digital
products make a direct integration of photogrammetry with
geographic information systems possible. In this sense,
PHODIS AT plays a very essential role for further automatic
procedures.
Table 1: PHODIS Product family
PHODIS Product | Photogrammetric Application
PHODIS SC photogrammetric scanning system
PHODIS AT automated digital aerotriangulation
PHODIS ST digital stereoplotting
PHODIS TS automatic DEM generation
PHODIS OP digital orthoprojection
PHODIS M monoplotting
PHODIS Base basic PHODIS tools
During the conception of PHODIS AT, special attention was
payed to the following aspects:
* Ease of operation,
* Handling of any block configurations,
* Handling of large blocks which cannot be measured in one
run due to the huge amount of data,
* Robust tools for the fully automatic determination of tie
points and the semiautomatic measurement of control and
new points,
Data compatibility with various block adjustment pro-
grams,
* Integration in the work flow of PHODIS and analytical
plotting systems controlled by programs such as PHOCUS
and P-CAP.
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B2. Vienna 1996
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