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EXPERIENCES WITH THE HELAVA AUTOMATED TRIANGULATION SYSTEM 
Thomas Kersten, William O’ Sullivan 
swissair Photo+Surveys Ltd. 
Dorfstr. 53, CH - 8105 Regensdorf-Watt, Switzerland 
Phone +41 1 871 22 22, Fax +41 1 871 22 00 
e-mail: [thomas .kersten, willi.osullivan] @srpv.ch 
Commission III, Working Group 1 
KEY WORDS: Aerial, digital, GPS, triangulation, bundle block adjustment 
ABSTRACT 
In this paper, we present our investigations and results on a digital aerial triangulation of two Swiss test blocks using 
the Helava Automated Triangulation System (HATS). In a pilot study, digital image data scanned with a resolution of 
25 um, from the block St. Gallen/Appenzell including 106 b/w images and from block Zug (82 b/w images), both at a 
photo scale of ca. 1: 27°000, were triangulated. The measurements were carried out on the Helava/Leica Digital 
Photogrammetric Workstation DPW770 each using a different tie point pattern. All observations were later adjusted 
in the GPS supported bundle adjustment program BLUH using self-calibration. The empirical accuracy from check 
points, which had not a very good quality due to their various sources, was better than 1 m in planimetry and in 
height using GPS photo centre coordinates and sparse ground control information in the combined adjustment. The 
RMS values of the GPS station coordinates were about 0.6 m in planimetry and 0.2 m in height. 
1. INTRODUCTION 
With the development of higher-resolution scanners, 
high quality digital imagery is increasingly available. 
Additionally, with the progress in high performance 
computer hardware and software, e.g. higher- 
resolution screens and faster image-handling 
capabilities, automation of photogrammetric processes 
becomes presently possible. Image processing and 
computer vision techniques have successfully been 
employed for facilitating automated procedures in 
digital aerial images such as interior orientation 
(Schickler, 1995; Lue, 1995; Kersten and Haring, 
1995), relative orientation (Schenk et al., 1990), point 
transfer in photogrammetric block triangulation 
(Tsingas, 1992), and the generation of Digital Terrain 
Models (Krzystek, 1991). 
The first digital photogrammetric system has been 
commercially available on the market since 1987. 
Today, with each new release, systems provide an 
increasing degree of automation in implemented 
photogrammetric procedures. In the past five years 
these systems are increasingly used in 
photogrammetric production to significantly improve 
the efficiency of the production processes. Specially 
in aerial triangulation, digital photogrammetric 
stations are surpassing conventional analytical plotters 
in accuracy and functionality, i.e. in the degree of 
automation in data capture and processing. Currently 
several commercial digital photogrammetric systems, 
e.g. Intergraph ImageStation, Leica DVP, DiAP from 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B3. Vienna 1996 
ISM, Helava/Leica DPW670 and DPW770 among 
others are available for photogrammetric production. 
To produce digital orthophotos for the entire area of 
Switzerland, swissair Photo4 Surveys Ltd. purchased 
digital photogrammetric equipment from 
Helava/Leica. For the project SWISSPHOTO blocks 
including in total 7800 colour resp. infrared photos 
must be processed within the next couple of years to 
meet the requirements of many customers in providing 
digital orthophotos as up-to-date basic data for various 
GIS applications. Consequentely this requires a high 
level of automation in all production processes, e.g. 
scanning, aerial triangulation, DTM and orthophoto 
generation, mosaicing, data management, etc., for 
efficiency, time and cost saving reasons. 
In this paper we present our investigations and results 
of a digital Aerial Triangulation (AT) of two blocks 
using the Helava Automated Triangulation System 
(HATS). The goal of a pilot study was to test the 
performance and the functionality of HATS. The 
object was to provide sufficient ground control to 
perform a traditional AT and compare the results with 
a GPS supported AT using GPS coordinates of the 
photo centres with a minimum amount of ground 
control points. Results of the GPS supported bundle 
adjustment and experiences with the functionality of 
HATS are presented. The advantages and 
disadvantages of HATS for automated digital 
triangulation under production conditions are also 
discussed in this paper. 
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