80
P. Wright
access detailed information on the composition and texture of the seabed, and
especially details of mine-like objects in the vicinity of shipping lanes.
Large
databases of oceanographic information are needed for anti-submarine warfare to
predict acoustic conditions in the deep oceans and surrounding shelf seas.
Each application listed in the preceding sections will have its own unique
requirements for data, but most will require some form of base data, either in the form
of a digital map or chart, to which other data can be referenced, or a digital elevation
model of the seabed.
TECHNICAL CONSIDERATIONS
The aim of the second stage of the HO/OS Coastal Zone Mapping Project was to create
a simple base map of the type referred to in the last paragraph of the previous section.
An area of Swansea Bay in South Wales was chosen for the experiment. The map
straddled the coastline and was created from existing map and chart data. Many of
the technical issues that had to be considered during this stage of the project apply to
the creation of any digital map or data set for use in GIS. These issues are considered
further in this section.
DATA AVAILABILITY
Very little hydrographic data is currently available for use in GIS, and still less is
marketed specifically for this purpose. This is not because there is no demand for the
data, but because at present few hydrographic offices have data readily available in a
form that is suitable for use in these systems. At present hydrographic offices are too
busy grappling with the difficulties of developing digital versions of their core
navigational products to be able to devote much time to creating datasets for use in
GIS. Priority is having to be given to producing digital data for use in electronic chart
display systems. However, in much the same way that raster electronic charts can be
produced as by-products of paper chart production, in future it should also be possible
to produce intelligent vector data for GIS as a by-product of vector electronic chart
production. In this way it should be possible to produce the data more cheaply than
would be the case if it was necessary to digitise the data specifically for this purpose.
Swansea Bay was chosen for the trial with the OS because at the time it was one of a
few areas for which the HO had digital data.
DATA QUALITY
Data quality is an important issue for most users of GIS.
Reliability, accuracy,
currency, completeness and consistency are all aspects of quality that are important in
this context. GIS users require data that they can trust to be correct. All data must
therefore be authenticated before it is supplied for use in GIS. Whether data is reliable
or not will depend to a large extent on its source.
P. Wright
access detailed information on the composition and texture of the seabed, and
especially details of mine-like objects in the vicinity of shipping lanes.
Large
databases of oceanographic information are needed for anti-submarine warfare to
predict acoustic conditions in the deep oceans and surrounding shelf seas.
Each application listed in the preceding sections will have its own unique
requirements for data, but most will require some form of base data, either in the form
of a digital map or chart, to which other data can be referenced, or a digital elevation
model of the seabed.
TECHNICAL CONSIDERATIONS
The aim of the second stage of the HO/OS Coastal Zone Mapping Project was to create
a simple base map of the type referred to in the last paragraph of the previous section.
An area of Swansea Bay in South Wales was chosen for the experiment. The map
straddled the coastline and was created from existing map and chart data. Many of
the technical issues that had to be considered during this stage of the project apply to
the creation of any digital map or data set for use in GIS. These issues are considered
further in this section.
DATA AVAILABILITY
Very little hydrographic data is currently available for use in GIS, and still less is
marketed specifically for this purpose. This is not because there is no demand for the
data, but because at present few hydrographic offices have data readily available in a
form that is suitable for use in these systems. At present hydrographic offices are too
busy grappling with the difficulties of developing digital versions of their core
navigational products to be able to devote much time to creating datasets for use in
GIS. Priority is having to be given to producing digital data for use in electronic chart
display systems. However, in much the same way that raster electronic charts can be
produced as by-products of paper chart production, in future it should also be possible
to produce intelligent vector data for GIS as a by-product of vector electronic chart
production. In this way it should be possible to produce the data more cheaply than
would be the case if it was necessary to digitise the data specifically for this purpose.
Swansea Bay was chosen for the trial with the OS because at the time it was one of a
few areas for which the HO had digital data.
DATA QUALITY
Data quality is an important issue for most users of GIS.
Reliability, accuracy,
currency, completeness and consistency are all aspects of quality that are important in
this context. GIS users require data that they can trust to be correct. All data must
therefore be authenticated before it is supplied for use in GIS. Whether data is reliable
or not will depend to a large extent on its source.