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Mapping the Environment through 3-Dimensional Space and Time
MORRIS, Kevin (K.Morris@ccms.ac.uk), Centre for Coastal and Marine Sciences, Plymouth Marine Laboratory, Plymouth, Devon, PL1 3DH, U.K.; and HILL, David and MOORE, Tony, Institute of Hydrology, Crowmarsh Gifford, Oxfordshire, OX10 8BB, U.K.
Key Words: 4-D, temporal, depth, mapping, information systems
Traditional geographical information systems (GIS) employ a 2-D, or, at best, 2.5-D framework, which is fine for many applications; however, mapping the environment introduces a number of problems that are not easily managed within existing systems. The natural environment is constantly changing and requires a more dynamic way of handling such data (one of the main problems facing temporal GIS (Kemp & Kowalczyk, 1994)). For instance, land-use may change from season to season or year to year. Similarly, the water-flow in a river is a constantly changing phenomenon. Environmental media, such as the oceans and the atmosphere, complicate matters further as processes that occur within them vary through 3-D space and time. In the past, time and depth have been handled as attributes to a feature. This can be very limiting as there is no ready dimensional structure against which features can be displayed or manipulated relative to time and depth. In nearly all conventional GIS, the x and y dimensions solely are used to display spatial data in map form at any one time. This paper describes a GIS system that handles time or depth visualization of a feature at the same time as mapping the feature horizontally. This treats time or depth as a dimension rather than an attribute, which is a prerequisite to effective multidimensional visualization and analysis (Raper & Livingstone, 1995).
The Space and Time Environmental Mapper (STEM) has been developed for Land-Ocean Interaction Study (LOIS), a U.K. research project investigating features and processes in the coastal zone. STEM is a GIS data viewer fronting a database containing the highlights of LOIS. STEM owes its flexibility to two key design objectives: a simple yet powerful query expression, retrieval and visualisation interface, and secondly, a generic database design that provides the core of the data-driven system. The database represents the real world in terms of objects (features) and properties (attributes). Both features and attributes can vary in space and time. The generic data model is interfaced to the application shell by a database application programming interface (DBAPI) that lies behind the query interface. The results of a query are returned to the interface shell for graphical presentation to the user where innovative display techniques make the exploration of relationships between objects and properties in the temporal and depth dimension achievable. The system incorporates time and depth bars to represent the additional dimensions. These bars act as an index to the data, and changing the time or depth on these bars will result in the display of the relevant x-y feature data in the mapping window. Alternatively, the multitemporal data can be animated and graphed.
Kemp, Z. and A. Kowalczyk, "Incorporating the Temporal Dimension in a GIS," in M.F. Worboys (ed.) "Innovations in GIS 1," (London: Taylor and Francis, 1994), 89-103.
Raper, J. & D. Livingstone, "Development of a Geomorphological Spatial Model Using Object-Oriented Design," (1995), 9: 4: 359-383.