2. TEST DATA AND PHOTOGRAMMETRIC
SYSTEMS USED
2.1. Test data
Two test blocks were selected comprising of ca. 2% of
the large block covering the entire area of
Switzerland. For the project SWISSPHOTO (Kersten
and O'Sullivan, 1996), Switzerland was flown in two
phases | using colour and infra-red films
simultaneously. In phase 1, the urban areas and the
northern part was flown from June to August, while in
phase 2 the Alps and all valleys in the southern part
were flown from August until October 1995.
The photo scale was approximately between 1: 24’000
and 1: 28'000 in the non-mountainous areas including
the separate flights in the southern valleys and
between 1: 34'000 and 1: 45'000 in the alps. During
the flights camera stations were recorded by DGPS
using a Leica GPS receiver in the airplane and at each
of three reference stations on the ground.
Additionally, 104 well distributed points of the new
Swiss GPS primary network LV'95 were signalized as
control points. Flight and block data are summarized
in Table 1.
For this pilot study 106 images (St. Gallen) resp. 82
images (Zug) at a scale of about 1:27'000 spread over
5 (6) parallel flight lines for each block were selected
covering the major part of the Cantons of St. Gallen
and Appenzell in the north-eastern region of
Switzerland and the whole Canton Zug. The flight
lines were flown from east to west and in the opposite
direction with an azimuth of ~20 resp. 200 degrees.
The dates and times of the flight lines varied from the
30.06.95 to 20.07.95 and from 7.25 AM to 12.44 PM
(UTC).
2.2. Hardware
The aerial triangulation was performed on a
Helava/Leica digital photogrammetric workstation
DPW770. All images were scanned on a Helava/Leica
Digital Scanning Workstation DSW200 in RGB mode.
The turn around time for scanning for each photo was
about 30 min. For triangulation the digitized colour
images were converted into greyscale images in order
to reduce disc space usage. The resolution of the
images was 25 um (1016 dpi), which corresponds to a
footprint of approximately 0.7 m on the ground, and
the size of each greyscale image was about 80 MByte.
Large portions of the approximately 75 GByte
available disc storage capacity were used for the
triangulation data.
2.3. Software
For the test block St. Gallen the software release
SOCET 3.1.6b (beta version) was used, while the test
block Zug was measured with the latest SOCET
3.1.1.2. version. HATS is a fully digital system for
performing block triangulation of suitably overlapping
images. The tedious process of selecting and
measuring image coordinates of pass and tie points is
highly automated, with the possibility of operator
override. The system flags unacceptable tie points and
Block 1 Block 2
Area: St. Gallen, Appenzell Zug
Area covered: ~1000 km’ 670 km’
Ground height: 400 - 1700 m 400 - 1900 m
Flying height a. s. 1.: - 4800 m - 4800 m
Camera: Wild RC30, 15/4 UAGA-F Wild RC30, 15/4 UAGA-F
Photo scale: -1: 27000 ~1: 27000
Forward/side overlap: 70%/30% 70%/30%
Number of strips: 5 6
Number of images: 106 82
Date of flight: 30.6.95/20.7.95 30.6.95/20.7.95
Film/digital imagery: colour diapositive/greyscale
Table 1: Flight and block data of the test blocks St. Gallen and Zug
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B3. Vienna 1996
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