4 Integration of Remotely Sensed Data into Geographical Infonnation Systems
79
to be focussed on the fundamental aspects of integration such as data generalization and accuracy specification.
To fully realize the potential of multi-sensor remote sensing for GIS in hydrology, more advanced integration techniques need to be developed. Several problems of a true integration of remote sensing and GIS could probably be solved by
recognition that GIS data and remote sensing data process and manage spatial
information at different levels of representation. Ultimately, a GIS and remote
sensing should be viewed as one entity that will be concerned with handling and
analyzing spatial data. Unification of these technologies will lead to a synergistic
integration of spatial data handling, and the final system would have more capabilities than just the sum of the two.
Hydrologic processes interact in three-dimensions (3D) between atmosphere,
land surface and sub-surface. Although many GIS can generate a 3D plot, no
commercial system has true 3D geometry and topology. Future developments in
GIS should concentrate on design and construction of a real 3D system so that
disparate databases can be integrated and analyzed in 3D as well as they are in 2D.
Hydrologic processes have a significant dynamic component. Recent applications have recognized the importance of change in hydrologic processes or input
model parameters over time. Time can be characterized as the fourth dimension of
the physical space-time continuum. However, we still cannot adequately represent
temporal dimension in GIS modeling (Langran, 1992), because no system currently handles chronology. We typically illustrate effects of temporal change as
slices of time for discrete intervals, but we need to show dynamic change over
continuous time. The ultimate solution would be to handle change in space as well
as change in time. An ideal GIS that handles time as a fourth dimension (4D GIS)
will have chronology treated much like topology; before and after taking on the
same importance as left and right in 2D space or above and below in 3D space.
Such a 4D GIS would be of immense value for a number of research areas in hydrology including soil moisture modeling, groundwater modeling etc. because of
their inherentfour-dimensional nature.
The 4D GIS technology should enable transparent access to heterogeneous hydrologic datasets and processing resources in intra- and inter-networked environments. A key component of such an interoperating system is the open interface
specification upon which the interoperating components are developed. The
OpenGIS Consortium is developing a comprehensive suite of OpenGIS specifications that provide a common Open Geodata Model framework and OpenGIS
Services Model to solve both technical and institutional non-interoperability
problems (Buehler and McKee, 1998). Future developments in the GIS world
should employ interoperating specifications to fully integrate and exploit both the
data and processing resources.
References
Bailey, R. G. (1988). Problems with using overlay mapping for planning and their implications
for geographic infonnation systems. Environmental Management, 12(1), 11-17
79
to be focussed on the fundamental aspects of integration such as data generalization and accuracy specification.
To fully realize the potential of multi-sensor remote sensing for GIS in hydrology, more advanced integration techniques need to be developed. Several problems of a true integration of remote sensing and GIS could probably be solved by
recognition that GIS data and remote sensing data process and manage spatial
information at different levels of representation. Ultimately, a GIS and remote
sensing should be viewed as one entity that will be concerned with handling and
analyzing spatial data. Unification of these technologies will lead to a synergistic
integration of spatial data handling, and the final system would have more capabilities than just the sum of the two.
Hydrologic processes interact in three-dimensions (3D) between atmosphere,
land surface and sub-surface. Although many GIS can generate a 3D plot, no
commercial system has true 3D geometry and topology. Future developments in
GIS should concentrate on design and construction of a real 3D system so that
disparate databases can be integrated and analyzed in 3D as well as they are in 2D.
Hydrologic processes have a significant dynamic component. Recent applications have recognized the importance of change in hydrologic processes or input
model parameters over time. Time can be characterized as the fourth dimension of
the physical space-time continuum. However, we still cannot adequately represent
temporal dimension in GIS modeling (Langran, 1992), because no system currently handles chronology. We typically illustrate effects of temporal change as
slices of time for discrete intervals, but we need to show dynamic change over
continuous time. The ultimate solution would be to handle change in space as well
as change in time. An ideal GIS that handles time as a fourth dimension (4D GIS)
will have chronology treated much like topology; before and after taking on the
same importance as left and right in 2D space or above and below in 3D space.
Such a 4D GIS would be of immense value for a number of research areas in hydrology including soil moisture modeling, groundwater modeling etc. because of
their inherentfour-dimensional nature.
The 4D GIS technology should enable transparent access to heterogeneous hydrologic datasets and processing resources in intra- and inter-networked environments. A key component of such an interoperating system is the open interface
specification upon which the interoperating components are developed. The
OpenGIS Consortium is developing a comprehensive suite of OpenGIS specifications that provide a common Open Geodata Model framework and OpenGIS
Services Model to solve both technical and institutional non-interoperability
problems (Buehler and McKee, 1998). Future developments in the GIS world
should employ interoperating specifications to fully integrate and exploit both the
data and processing resources.
References
Bailey, R. G. (1988). Problems with using overlay mapping for planning and their implications
for geographic infonnation systems. Environmental Management, 12(1), 11-17