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in the not too distant future. Setting up a data infrastructure
sufficient attention should be given to airborne data supply.
Recent and present developments with respect to processing
algorithms and data-integration should be incorporated within the
European and national data-infrastructures. A number of stages of
processing can be identified in this respect:
- preprocessing (e.g. geometric and atmospheric correction)
- processing (e.g. algorithm for deriving water quality
parameters)
- post-processing (e.g. integration of remote sensing derived
water quality products with numerical models and GIS)
The functional design of a data infrastructure for water quality
applications is presented in figure 1. Operational use of remote
sensing not only depends on the availability and flexibility of
(spaceborne and airborne) platforms, but also on an efficient
processing chain of the data. As compared to spaceborne data,
(pre-)processing of airborne data is even more complex,
especially with respect to geometric and atmospheric correction
and corrections for the air-water interface. In general airborne
remote sensing benefits from incorporation of a real-time dGPS
system in the airborne platform, which will significantly reduce
the pre-processing time.
Standard toolkits will not only reduce the time delay between
acquisition and delivery of information to the end user, but also
give more objective quality labels to the remotely sensed
information. It is recommended to implement standard remote
sensing (pre-)processing tools as public domain software at a
number of governmental and commercial companies.
In general, during the summer months, a number of regional and
local water managers are interested in remote sensing based water
quality information of their region. A main bottleneck is that these
water managers are not familiar with practical aspects related to
the conditions for remote sensing flights. Furthermore, airborne
remote sensing on a project basis for individual clients is in
general too expensive. Consequently, operationalization of
airborne remote sensing for water quality would benefit from
coordinated data-acquisition, in which a value added company (or
a consortium) contacts regional and local water managers,
coordinates flights during the summer months, asks for offers
from candidate airborne data-providers, distributes the raw data to
(other) value added companies, etc.
Internet WWW will play a very important role in the future
satellite data infrastructure. Almost all satellite data providers are
currently building meta information systems, including quick
look browsing facilities. This development will have a
tremendous impact on the accessibility of satellite data for the
users. Satellite data sets have large volumes. Currently transfer of
satellite data through Internet is not an option, although for
smaller data volumes Internet technology can already be used
(e.g. processed ERS SAR data for near real time oil spill
detection). However, as high speed computer links will enable
near real-time data distribution within a few years from now, the
user group of "water quality" satellite data should keep an eye on
these fast developments.
In an European context (CEO) and at national and institutional
levels, meta information systems have to be developed, which
form an information shell around data base systems containing
remote sensing imagery. These shells must provide entrances and
links to the actual data base systems where (raw) remote sensing
13
data is kept. Furthermore, advertising the potentials of remote
sensing through the Internet could create new users and products
and stimulate (inter-)national cooperation between research
groups and water quality managers. In this respect the EARSeL
SIG on "marine waters, inland waters and coastal zones" can play
a role in the context of CEO.
3. COASTAL MORPHOLOGY
3.1 Management problems
For sustainable development and management of sedimentary
coastal plains, reliable and up-to-date geomorphological infor-
mation is needed on the bathymetry of the near coastal zone and
the height of the beach and coastal dunes. In this context for the
manager of these lowland areas two main tasks can be identified:
1) management and maintenance of shipping lanes to ensure
transport and distribution capacity and 2) protection of the in-
shore area against flooding.
For safety, efficiency and economic reasons there is a need for
accurate and reliable depth information in navigation areas. With
respect to the required type of bathymetric information a
distinction can be made between two types of in-situ depth
measurements: 1) monitoring of large scale morphodynamics and
2) small-scale surveys for management in depth-critical areas.
Monitoring surveys are carried out to support long-term safety
strategies. Depth measurements in shipping areas and dump
locations contribute to short-term management and maintenance
and they have a strong relationship with economic and legal
responsibilities of the authorities.
In most lowland countries the foredunes, beaches and near coastal
zone are monitored on a regular basis to assure that their primary
function as defence against the sea is maintained. For instance in
the Netherlands, as of 1964 the topography of the coast is
measured in cross sections perpendicular to the coast line. The
measurements consist of depth measurements of the near coastal
zone and height measurements of the beach and foredunes. In
total 1700 of such coastal profiles are measured yearly, through
acoustic measurements and standard analytical photogrammetric
means. Based on these observations it is decided where and how
much sand is to be supplied. For the part five years, in the
Netherlands "the dynamic maintenance of the coast line" is the
guiding principle, indicating that some freedom is allowed for the
dynamic processes to take place.
Knowledge of the actual depth of the sea bottom and shipping
lanes and the height of the coastal defense works is fundamental
to take corrective actions, if necessary. In practice this means that
either sand nourishment or channel dredging is carried out. On a
long term basis morphodynamical information is used to make
predictions of future morphological changes. This type of
information is used to formulate a long-term strategy towards
coastal defense matters.
Besides its function to protect the lowland against flooding, the
sandy coastal area unites a number of other important functions.
The dune area serves as an important reservoir proving drinking
water to cities. Another important aspect concerns tourism and
recreation. Also claims are exerted on the coastal area with respect
to housing, industrial and agricultural activities. And, last but not
least, the coastal zone is of paramount importance in view of the
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B6. Vienna 1996
