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laser scanning for elevation measurement and airborne video 
for thematic data in time. The laser scanning is to replace the 
traditional photogrammetric approach to obtain profiles of the 
beach and foredunes (see figure 3 and 4). These techniques 
seem to be much more promising for these kind of areas then 
digital photogrammetry: the lack of texture doesn't influence 
the accuracy of laseraltimetry data badly, and the little objects 
to be gathered by vectors won't need high precision images like 
(scanned) photographs. 
As of 1996, a DEM of the beach and foredunes of the Dutch 
coast will be provided annually, based on laser scanning data. 
Also, once every year the complete coastal zone (incorporating 
dunes) will be surveyed. Video data will provide information 
on e.g. vegetative cover, development and migration of blow- 
outs. In addition, by means of bird's-eye-views a good visual 
impression of the coastal area is obtained (Huising and 
Vaessen, 1996). 
4.2.3 Road network database The appearance of the final 
product 'road network database' is mostly as desired by the 
users. À major problem is to keep this database up-to-date, i.e. 
all roads and existing streets are present in the database, and 
streets and roads which are changed in position, are moved in 
the database. 
Photogrammetry could be a suitable technique for updating the 
database, in particular digital photogrammetry giving the 
opportunity to use low-cost pc-systems in stead of expensive 
analytical plotters or analogue stereoscopes. 
During 1994 and 1995 we carried out a test using our pc- 
mapping system DVP of Leica, and scanned aerial photographs 
scale 1:18.000. This small scale basis product accompanied 
with a comparative low-accuracy mapping system, delivered a 
relatively cheap update process; the human power costs are 
about $ 0.6 million and the costs for the instruments used are 
about $ 0.05 million (Wicherson and Van der Kraan, 1995). 
4.3 Future expectations 
At this moment at least two other topics are in view for using 
digital photogrammetry efficiently in the future: automatic 
2. 
dr 
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Figure 3: Beach profile, as currently produced 
aerotriangulation, substituting semi-automatic aerotriangulation 
performed on the DCCS, and generating vegetation maps 
digitally. 
4.3.1 Automatic aerotriangulation Many reports that have 
been published during the last years give an optimistic prospect 
of the operational use of automatic aerotriangulation, see for 
example (Tang and Heipke, 1996). The DPW-770 of Leica 
provides a module for automatic aerotriangulation. We tested 
this module extensively during our benchmark in 1995, and the 
earliest results were promising indeed. Subsequently we will 
carry out extended tests in 1996, and if these tests bear out our 
careful optimism, we can substitute the DCCS by a stripped 
version of the DPW-770, embodying only the most necessary 
modules for automatic aerotriangulation. 
4.3.2 Digital vegetation maps As described in chapter 2, the 
vegetation maps are only available in digital format at the very 
end of the process. This mainly analogue process can be sub- 
stituted by a digital-photogrammetrical process, probably with 
rather much profit. 
The idea is to scan false colour photographs and to use a pc- 
based photogrammetric mapping system, like our DVP. 
Advantages of using digital images and techniques above our 
current process using analogue images and techniques, are the 
possibilities to use old vector maps for superimposing purposes 
and to fasten up the internal process by removing the stage of 
scanning, skelettonizing, vectorising and correcting the vector 
map. Moreover the possibility arises to quantify vegetation 
types by using (semi-)automatic multi-spectral classification as 
an extra product. 
Despite these advantages, we still don't use digital photo- 
grammetry because of some technical problems (huge storage 
capacities needed) and other organising aspects, like starting 
problems resulting in loss of production, and minor importance 
given to implement this technique in our production 
environment at the moment. 
  
Figure 4: Laseraltimetry DEM of a part of Ameland, heights are 
represented in grey values. 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B4. Vienna 1996