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3.1 Hardware developments
The digital photogrammetric workstations, too, have
migrated to the Sun Ultra 1. The Fast Frame Buffer of
the Creator 3D Model 170E gives a practical, off the
shelf solution for stereoscopic viewing and smooth
roaming. Similarly, the Silicon Graphics Indigo? with its
XL, High Impact and Solid Impact graphics engines
provides an excitingly powerful platform and SOCET
SET has ported easily to the dual head versions of the
lower level SGI Indy. Monoscopic and split screen stereo
workstations are available on many models of Ultra,
Indigo? or Indy and at the time of writing the
SPARCstation 20 and SPARCstation 5 Model 110 were
being retained owing to their economy. Like the
DSW200 and DSW300, the workstations are supplied
with 6 GB hard disk capacity and use 8 mm tape
cartridge drives for longer term storage. The hardware
environment has also been enhanced by a new hand
controller based on mouse technology as opposed to the
mechanical, rack and pinion approach in the earlier
model, transplanted from the Leica SD2000/3000 line.
3.2 SOCET SET software
The SOCET SET software has been incrementally
enhanced. Its current structure, including some Leica
and third party packages for map compilation and DTM
manipulation, is schematised in Figure 2.
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Figure 2. Structure of SOCET SET and related modules
3.2.1 CORE SOCET. The same automated interior
orientation and JPEG compression as the scanners have
been added. All operations throughout the SOCET SET
suite are now available for 8-bit greyscale and 24-bit
colour imagery. The range of image, vector and DTM
69
formats capable of being imported and exported has
increased over the years. A useful feature for some
customers is the model manager, whereby pairs of
orientated images may be defined as stereo models,
between which the user can switch by means of a single
menu selection. This operation takes one to two seconds
and thus outperforms analytical stereoplotters with large
stage plates. Moreover, more than two models can be
handled at once.
3.2.2 Satellite imagery. The use of data from JERS-1
was added in 1995 and a module for IRS-1C is in
preparation.
3.2.3 Automated triangulation. A major new SOCET
was introduced in 1995, called HATS (Helava
Automated Triangulation System). Accounts have been
given by Miller and Walker (1996) and De Venecia et al.
(1996). The basis of the module is automated
measurement of control, pass and tie points by area
based image matching. The ground control points must
be measured manually in at least one image and set up
procedures exist to inform the system of the
configuration of the block and the forward and side
overlaps. The latter are much abbreviated when GPS
coordinates of exposure stations are input. Cross strips,
different photo scales and mixed aerial and satellite
imagery are all possible. After the matching, interactive
editing may be invoked to repair failure cases. Numerous
blunder checks exist, from simple model, strip and block
formation to data snooping after the built-in bundle
adjustment. Indeed, at least one user has successfully
minimised the interactive phase by going for very large
numbers of tie points and making no attempt to measure
failure cases manually, though of course gross errors
must still be eliminated. It is also possible for users to
output image coordinates from HATS to their existing
block adjustment packages, for example ALBANY and
PAT-B. Thus far it appears that the whole process takes
around 10 minutes per image, which must be compared
to the preparation, point marking and transfer,
measurement, adjustment, re-measurement and final
adjustment phases of analytical triangulation. Some early
experiences have been reported by De Venecia et al. (op.
cit.) and Kersten (1996). Current work centres on
improvements to the user interface and expansion of the
GPS facilities, such that a wide range of popular formats
can be read and the bundle adjustment includes drift
parameters.
3.2.4 Close range photogrammetry. Special software
has been added for the orientation of close range images,
including automated generation of initial values, an
extended mathematical model, tracking in directions
other than ground XYZ and rectification for viewing into
user defined planes. The key is the transfer of image
coordinates observed with standard SOCET SET
functions to the PRIORI and CAP modules ported from
the MAAS-CR software available for the Leica analytical
plotters (Hinsken ef al., 1992).
3.25 DTMs, orthophotos and mosaics. There are
additional strategies for automated DTM generation,
together with new, interactive editing tools. Batch
merging with planimetric data provides a powerful
editing method too. Tests have proved the DTMs to be
good enough for change detection, for example to
monitor urban development or to estimate timber
volumes through measuring tree growth. The latest
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B2. Vienna 1996
