Another drive comes from our customers: they wish complete 
databases, suitable for integral management. 
4.2.1 New data sets for monitoring river areas In 1995 we 
restarted a project for developing new products for integral 
management for the river areas using digital photogrammetric 
techniques, in particular (semi-Jautomatic DEM, orthophoto 
and  bird's-eye-view generation. The reason for this 
development push are among others the problems caused by the 
river floods in The Netherlands in 1993 and 1995. The need for 
hydrodynamic models became clear, and these models require 
up-to-date height and roughness information of the river areas, 
as these two aspects influence the stream velocity and water 
capacity most. 
The river areas consist mainly of pastures, surrounded by dikes, 
river-banks and the river itself. Next to that other objects are 
buildings, roads et cetera. Height information is one of the most 
important parts of the river databases. 
We expected a serviceable use of digital photogrammetry for 
this product for several reasons: 
- the main area of interest for the river databases (pastures, 
overgrown dikes) is very suitable for automatic DEM 
matching techniques. Especially if the resulting raster DEM 
is completed with the most important break lines, the 
resulting DEM is highly densed and of high accuracy, made 
without much human effort; 
- asignificant part of the vectors to be gathered in the present 
river databases are mainly meant for easier interpreting the 
  
Figure 1: Part of the river database; the most relevant features 
are represented by vectors, and in addition single 
height points are measured. 
946 
databases. Making an orthophoto delivers at least the same, 
but likely more information for interpretation purposes. 
Therefor, making an orthophoto would save time which is 
now used for gathering vectors meant for interpreting 
purposes (see figure 1 and 2); 
- the addition of bird's-eye-views makes the final product 
more attractive. These products can be used for 
presentations of plans for citizens and other parties 
concerned. 
Next to the above mentioned advantages, the digital photos can 
be used for accurate mapping, either on digital or analytical 
instruments. Moreover, the acquisition of thematic information, 
like a land use classification, can be executed directly. 
This digital photogrammetric work will be carried out in a 
production environment using a DPW-770 of Leica, purchased 
at the beginning of 1996. 
Probably airborne laseraltimetry in combination with video 
images provides us data which is accurate and complete enough 
for the purposes mentioned above. In a project currently carried 
out, we take a closer look at the potentials and we make 
comparisons between laseraltimetry, video, digital photo- 
grammetry and satellite remote sensing in terms of efficiency. 
4.2.2 New data sets for monitoring coastal areas Last year 
the MD launched a proposal for the introduction of new 
techniques for the acquisition of elevation data and thematic 
imagery of the coastal zone. The techniques consist of airborne 
  
Figure 2: Part of the new river database: an orthophoto for as 
underground for interpreting reasons and the main 
vectors, additioned with a highly densed DEM 
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