These costs alone (ignoring the costs associated with the training and employment
of personnel) are often prohibitive, restricting GIS to developed countries
or large commercial concerns. The second reason concerns the
dynamics of aquatic systems. Aquatic systems are more complex and dynamic
than terrestrial domains and, therefore, require different types of
information, both in terms of quality and quantity. The aquatic environment
is typically unstable and needs to be recognized as a 3D (spatial) or
even a 4D (spatiotemporal) domain. Mapping 4D information (3D + time) is
difficult and is often not tackled for this reason. Third, while many commercial
software developers have incorporated advanced statistical tools
into their packages, there has always been a terrestrial bias, particularly
with regard to systems developed for commercial applications. As a result,
no effective GIS software is available for handling both fisheries and oceanographic
data as it involves resolving problems associated with database
storage and graphical representation of heterogeneous vector and raster
data sets.