sensor 
oint will 
to view 
a nadir 
directly 
e DTM 
image 
nto an 
WS are 
as this 
on with 
curious 
d! It is 
je map 
ting. 
primary 
1) or a 
ecision 
I asa 
cation 
part of 
ousing 
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, slope 
able to 
ct (ie. 
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Iso be 
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most 
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use a 
based 
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usand 
ind for 
ap and 
nputer 
y the 
using 
stereo imagery, as this was the only. way to get accurate x, 
y & z map information, unaffected by relief distortion. 
Today, the operator can simply use the mouse to digitise 
vector map information (and attributes) directly from the 
orthoimage on screen, using the computer as a 
"monoplotter". This de-skills the entire vector generation 
process and hence reduces the cost of creating the 
database. As this is normally the major cost component of 
a GIS system , softcopy photogrammetry is a way of 
reducing that cost. 
3D GIS 
Finally, a glimpse into the future. The computer world as we 
know it is becoming a 3D world. No longer are simple 
planimetric views enough, with users demanding 
perspective views and real time flythroughs. in Autumn 95, 
ERDAS will be releasing its own real time 3D Viewer called 
IMAGINE Virtual GIS, which will allow DTMs generated in 
IMAGINE OrthoMAX (or from anywhere else) to be flown 
around in real time. Vectors (such as ARC/INFO 
coverages), symbols and annotation can also be draped 
and flown around. One unique feature of the software will 
be the 3D GIS capability, which allows the 3D image to be 
queried in real time. Essentially, it will provide all the 
functionality of a 2D GIS but in 3D! This is the first step in a 
new direction in GIS where the real world can be modelled, 
analysed and queried in 3D on the desktop. 
CONCLUSION 
It is easy to appreciate the advantages that are brought to 
the production of terrain databases and derived products 
such as orthoimages with the introduction of well developed 
73 
software algorithms, combined with the increasing 
availability of powerful desk top workstations. It is however 
fair to say that despite these tremendous advances, there 
is still a significant caution in the user community and there 
are many published technical evaluations that bear witness 
to this. Without doubt however, digital systems are here to 
stay and are being constantly improved. They have already 
proved that they offer significant improvements in 
production throughput and their ability to operate with 
minimal operator intervention will certainly mean that 
reduced production costs can be easily achieved. It is 
anticipated in the future that fully automated systems will be 
available, requiring not only less operator time, but less 
skilled operators. As systems become easier to use, so the 
technology will be more accessible to a wider range of end 
users, who traditionally were excluded from undertaking 
photogrammetric projects by virtue of the technical 
complexity and the level of operator training. 
From the application engineers perspective, it is now 
possible to generate digital terrain models and orthoimages 
as and when required on standard commercially available 
hardware. More importantly, the information can be 
generated on demand to the exact density, area and quality 
required by the particular project, and as all GIS users 
know, having the correct data in place on day one is the 
first major step towards a successful project. 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B4. Vienna 1996