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D.R. Green and S.T. Ray
GEOREFERENCING
Datasets are often provided as either grid coordinates or latitude and longitude.
Therefore a first step is to convert all the datasets to a single common coordinate
system. If they are all supplied in the same coordinate system, this will enable more
efficient data loading and once again there is less room for error to creep in.
MULTIPLE SOURCES
Data in any environmental application may ultimately come from many different supply
sources. As a direct result the dataset will contain many variations e.g. some topics or
themes will be very well covered with very detailed datasets for many years and
locations, whilst other topics will have been recorded for a restricted number of sites
and with insufficient temporal resolution. This means that many data coverages will not
be directly comparable thereby limiting their potential for procedures such as GIS
overlay mapping analysis. Many datasets may indeed contain more or less the same
data on overlapping regions, therefore being a duplication of both cost and effort and
limiting the potential for sharing of the datasets between organisations.
FORMAT
Another critical factor is the format in which the datasets are provided. Due to the
likely different nature of data from different sources, for which there is no requirement
for adherence to a standard, there will be many formats. ArcInfo export files tend to be
preferred but more typically data comes in the form of formatted ASCII (either
geographical - latitude/longitude - or National Grid), paper lists/tables (which have to
be inputted by hand), DXF, DBase, and paper maps (requiring digitising). Many
datasets are obtained in a format which can only feasibly be converted into one or other
of points, arcs or polygons (points, lines, areas). A variety of data conversion
procedures therefore have to be adopted with extensive use often being made of
software such as Microsoft Excel followed by the use of ArcInfo routines.
FEATURE TYPE/INTERPOLATION
Many coastal datasets are collected at point sources directly on the coast and can not
therefore be interpolated or extrapolated into the marine zone if needs be. Equally there
are too few primarily marine datasets and this can prove very restrictive for any spatial
analysis. Few datasets appear to be acquired in a digital format that can lead to complex
and time-consuming data conversion procedures. Due to survey collection methods of
original data some material can have very low precision, both in the survey and for the
sample locations. There is also very little information about the actual sources of the
data, collection techniques, quality, and known errors. Some potentially useful datasets
are of restricted value due to their one-off survey characteristics and the limited spatial
locations and time-periods for which they were available.
D.R. Green and S.T. Ray
GEOREFERENCING
Datasets are often provided as either grid coordinates or latitude and longitude.
Therefore a first step is to convert all the datasets to a single common coordinate
system. If they are all supplied in the same coordinate system, this will enable more
efficient data loading and once again there is less room for error to creep in.
MULTIPLE SOURCES
Data in any environmental application may ultimately come from many different supply
sources. As a direct result the dataset will contain many variations e.g. some topics or
themes will be very well covered with very detailed datasets for many years and
locations, whilst other topics will have been recorded for a restricted number of sites
and with insufficient temporal resolution. This means that many data coverages will not
be directly comparable thereby limiting their potential for procedures such as GIS
overlay mapping analysis. Many datasets may indeed contain more or less the same
data on overlapping regions, therefore being a duplication of both cost and effort and
limiting the potential for sharing of the datasets between organisations.
FORMAT
Another critical factor is the format in which the datasets are provided. Due to the
likely different nature of data from different sources, for which there is no requirement
for adherence to a standard, there will be many formats. ArcInfo export files tend to be
preferred but more typically data comes in the form of formatted ASCII (either
geographical - latitude/longitude - or National Grid), paper lists/tables (which have to
be inputted by hand), DXF, DBase, and paper maps (requiring digitising). Many
datasets are obtained in a format which can only feasibly be converted into one or other
of points, arcs or polygons (points, lines, areas). A variety of data conversion
procedures therefore have to be adopted with extensive use often being made of
software such as Microsoft Excel followed by the use of ArcInfo routines.
FEATURE TYPE/INTERPOLATION
Many coastal datasets are collected at point sources directly on the coast and can not
therefore be interpolated or extrapolated into the marine zone if needs be. Equally there
are too few primarily marine datasets and this can prove very restrictive for any spatial
analysis. Few datasets appear to be acquired in a digital format that can lead to complex
and time-consuming data conversion procedures. Due to survey collection methods of
original data some material can have very low precision, both in the survey and for the
sample locations. There is also very little information about the actual sources of the
data, collection techniques, quality, and known errors. Some potentially useful datasets
are of restricted value due to their one-off survey characteristics and the limited spatial
locations and time-periods for which they were available.