Technical aspects of data acquisition and display
Projects goals
The first example is an operational project of data acquisition, which
took place in 1994 on the demand of waterworks companies. The water
company of the city of Amsterdam (Gemeentewaterleidingen Amsterdam, GWA) and the waterworks service of the region North Holland
(Waterleidingbedrijf Noord-Holland, PWN) chose the laser scan technique to acquire a DTM of their control areas. The surveyed areas were
situated along the North Sea coast covering an area of 40 km by four kilometres. The GWA and the PWN needed a DTM of their control areas for
many uses. A first example was the use of the DTMs for re-structuring
projects, to determine ground resistance. A second example was the
production of maps with an accurate rendering of the relief for orientation in the field. DTMs were also needed to integrate elevation data in
a hydraulic model of the dune area to permit the study of the effect of
water extraction from the dunes on the flora and fauna in the frame of
hydro-ecological research. In this study, the water height uncler ground
level plays an important role. The combination of ground level with a
vegetation map and the depth of the ground water by means of water
company’s GIS provided an accurate image of the possible development of the natural dune vegetation, while it permitted hydrologists
a better evaporation determination. Water works companies also wanted
to use the DTMs as basic information for relief dune spontaneous
changes monitoring and for geomorphology studies of the dune vales
and dune ridges (Han, 1995).
The second example is an operational project, which took place in
1996, 1998 and 1999 to acquire elevation data for the Survey Department.
The Survey Department, which is part of the Directorate General of
Public Works ancl Water Management is responsible to provide geoinformation for coastal defence, infrastructure and river management
in the Netherlands. For this reason the Survey Department has been
undertaking yearly measurements of the Dutch coast to monitor the
structural regression of the coastline in order to take active measures
to preserve the coastline and for purpose of coastal defence. As explained
by Huising & Vaessen (1997b), these yearly measurements used to be
performed by means of photogrammetry in measuring profiles every
200 m along the coast, permitting to establish the position of the coastline. The photogrammetric process was time consuming and expensive.
For this reason the Survey Department sought for an alternative technique
for elevation determination. This research led the Survey Department to
opt in 1995 for the laser scan technique to perform their yearly survey
of the Dutch sedimentary coast, providing data for coastal defence
purposes and coastal erosion assessment. With a new DTM every year,
the Survey Department is able to model the yearly variations of coast
morphology due to wind and sea action.
153
Projects goals
The first example is an operational project of data acquisition, which
took place in 1994 on the demand of waterworks companies. The water
company of the city of Amsterdam (Gemeentewaterleidingen Amsterdam, GWA) and the waterworks service of the region North Holland
(Waterleidingbedrijf Noord-Holland, PWN) chose the laser scan technique to acquire a DTM of their control areas. The surveyed areas were
situated along the North Sea coast covering an area of 40 km by four kilometres. The GWA and the PWN needed a DTM of their control areas for
many uses. A first example was the use of the DTMs for re-structuring
projects, to determine ground resistance. A second example was the
production of maps with an accurate rendering of the relief for orientation in the field. DTMs were also needed to integrate elevation data in
a hydraulic model of the dune area to permit the study of the effect of
water extraction from the dunes on the flora and fauna in the frame of
hydro-ecological research. In this study, the water height uncler ground
level plays an important role. The combination of ground level with a
vegetation map and the depth of the ground water by means of water
company’s GIS provided an accurate image of the possible development of the natural dune vegetation, while it permitted hydrologists
a better evaporation determination. Water works companies also wanted
to use the DTMs as basic information for relief dune spontaneous
changes monitoring and for geomorphology studies of the dune vales
and dune ridges (Han, 1995).
The second example is an operational project, which took place in
1996, 1998 and 1999 to acquire elevation data for the Survey Department.
The Survey Department, which is part of the Directorate General of
Public Works ancl Water Management is responsible to provide geoinformation for coastal defence, infrastructure and river management
in the Netherlands. For this reason the Survey Department has been
undertaking yearly measurements of the Dutch coast to monitor the
structural regression of the coastline in order to take active measures
to preserve the coastline and for purpose of coastal defence. As explained
by Huising & Vaessen (1997b), these yearly measurements used to be
performed by means of photogrammetry in measuring profiles every
200 m along the coast, permitting to establish the position of the coastline. The photogrammetric process was time consuming and expensive.
For this reason the Survey Department sought for an alternative technique
for elevation determination. This research led the Survey Department to
opt in 1995 for the laser scan technique to perform their yearly survey
of the Dutch sedimentary coast, providing data for coastal defence
purposes and coastal erosion assessment. With a new DTM every year,
the Survey Department is able to model the yearly variations of coast
morphology due to wind and sea action.
153