Knowledge about the currency of the data and the frequency of updates is also vital,
especially if different datasets acquired on different dates are being used. Provision of
this information in the metadata is vital, and knowing when a dataset was collected,
how, and when it was updated is often information that is not available.
UPDATING
Using GIS for Siting Artificial Reefs
125
brings related problems of data security, overloading the system, IT support, as well as
complications with the licence agreements.
SIZE
The size of the data files is always important in any GIS project. However, it is more
important in a small organisation with limited disc storage space. The requirement for
more frequent backups and data management therefore becomes necessary. Large raster
datasets, e.g. satellite imagery, take up a great deal of disk space, and require powerful
computer systems to both display and analyse the datasets.
ORIGINAL USE/PROJECT AIMS
In most cases, datasets that are already available usually form the basis for many new
projects and applications. One argument used to justify this is that they have multiple
potential uses, are already available, do not require additional expenditure, and avoid
unnecessary duplication of effort. However, many environmental datasets are in fact
acquired for a specific purpose (small projects and are not part of a larger data
acquisition strategy), and not the one that individuals find a new use for. Whilst some
applications can make use of these, others may find that they are incompatible with
other datasets, are of the wrong scale, and so on. Due care and attention must therefore
be exercised in the use of archival data and those not acquired specifically for a new
project.
METHOD OF DATA CAPTURE
Knowing something about the method of data capture is very important, particularly for
a pilot application. Data capture might have been undertaken by trained professionals
carrying out surveys to specific requirements, or by amateurs with no real sense of
accuracy for fieldwork. The quality of the data may therefore be suspect. This problem
can also apply to the data loading, with reference to digitising, scanning, and data
import using software packages other than those used originally. These methods of data
capture will all lead to many errors which then accumulate throughout the import
process. In addition, the provision of a record of the entire process (e.g. a log file) is
very important in tracing and identifying a weak link, or a potential source of large
errors in the final results. Boats, for instance, with satellite tracking devices, although
getting better, are possibly less accurate than a surveyed portion of the coastal strip.
Awareness of this and consideration in the GIS use and analysis must all be taken into
account.
especially if different datasets acquired on different dates are being used. Provision of
this information in the metadata is vital, and knowing when a dataset was collected,
how, and when it was updated is often information that is not available.
UPDATING
Using GIS for Siting Artificial Reefs
125
brings related problems of data security, overloading the system, IT support, as well as
complications with the licence agreements.
SIZE
The size of the data files is always important in any GIS project. However, it is more
important in a small organisation with limited disc storage space. The requirement for
more frequent backups and data management therefore becomes necessary. Large raster
datasets, e.g. satellite imagery, take up a great deal of disk space, and require powerful
computer systems to both display and analyse the datasets.
ORIGINAL USE/PROJECT AIMS
In most cases, datasets that are already available usually form the basis for many new
projects and applications. One argument used to justify this is that they have multiple
potential uses, are already available, do not require additional expenditure, and avoid
unnecessary duplication of effort. However, many environmental datasets are in fact
acquired for a specific purpose (small projects and are not part of a larger data
acquisition strategy), and not the one that individuals find a new use for. Whilst some
applications can make use of these, others may find that they are incompatible with
other datasets, are of the wrong scale, and so on. Due care and attention must therefore
be exercised in the use of archival data and those not acquired specifically for a new
project.
METHOD OF DATA CAPTURE
Knowing something about the method of data capture is very important, particularly for
a pilot application. Data capture might have been undertaken by trained professionals
carrying out surveys to specific requirements, or by amateurs with no real sense of
accuracy for fieldwork. The quality of the data may therefore be suspect. This problem
can also apply to the data loading, with reference to digitising, scanning, and data
import using software packages other than those used originally. These methods of data
capture will all lead to many errors which then accumulate throughout the import
process. In addition, the provision of a record of the entire process (e.g. a log file) is
very important in tracing and identifying a weak link, or a potential source of large
errors in the final results. Boats, for instance, with satellite tracking devices, although
getting better, are possibly less accurate than a surveyed portion of the coastal strip.
Awareness of this and consideration in the GIS use and analysis must all be taken into
account.