GEO 465/565 - Lectures 13 & 14
3D and Temporal GIS


although vast majority of GISs currently work only in 2 dimensions, across the plane . . .

certain applications require the addition of other dimensions, namely elevation/depth or time

3D Applications

engineering design of mines, quarries, dams, reservoirs, etc.

geological/geophysical exploration

scientific explanation of 3D processes such as ocean currents or lava flows

data driven - may not necessarily know what you will find in 3D

so the structure of the representation may enhance types of analyses that can be performed

The Vertical Dimension

two very different ways of looking at representations of the vertical dimension (third dimension) in GIS

2.5-D and 3-D

vertical dimension combined with temporal query = 4-D

2.5 D

most common way of doing 3D in commercial GIS packages

z value (normally elevation) is recorded as an attribute for each data point (x,y)

z values can be used in a perspective plot to create the appearance of 3 dimensions

not true 3-D representation because elevation is not part of the object's data structure, is not encoded in the topology of an elevation point

system can accept only 1 z value for any surface at a given location

2.5 D Representations

attractive way of displaying topography and other continuous surfaces from DEMs or TINs

perspective plots computed from any viewpoint

additional layers "draped" over the surface using color

"artist's impressions" - convert classes (e.g., land cover) to simulated trees, etc.


The files below are in MPEG format.

True 3-D

store data in structures that actually reference locations in 3D space (x,y,z)

here z is not an attribute but an element of the location of the point

data can be recorded at several points with equal x and y coordinates, e.g.,

soundings in the ocean or atmosphere, geologic logs of wells

Boundary Representation

objects are defined as polyhedra bounded by planes or faces

each object can be represented by a number of faces, edges, points

TIN is a 2.5 D type of B-rep, constrained to be single-valued (i.e. one value of z for every x,y)

B-Rep of a Cave Passage


requires a powerful user-interface to construct combinatorially-complex objects

each part of the B-rep (planes, edges, points) must be carefully and consistently

defined for each application in order to maintain validity

performance degrades rapidly with high geometric complexity


visualization of volumes

modeling of volumes

algorithms for 3D spatial analysis simpler, more efficient, if data in a volumetric form

Spatial Occupancy Enumeration (SOE)

volume is divided into cubes or voxels

usually produced by converting from B-reps (similar to converting vectors to rasters in 2D)

properties like mass, volume and surface area are quickly computed as

Boolean operations [on (full) / off (empty)] or voxel counts

SOE of a Mine/Quarry

Commercially Available?

these 3D representations are relatively new, so there is little collective experience on how to implement them in the earth sciences and engineering not too many truly 3D GIS packages on the market

2- or 2.5D GIS linked to 3D modeling package

Related Technology

may be easiest to utilize technology developed in other fields (e.g., mechanical engineering, medicine)

HOWEVER, needs of these fields different from earth sciences

Medical Imaging Example

not designed for modeling, doesnt need analytical tools for abstraction and interpretation that earth science applications do

time dependent (need to track moving objects between one 3D image and the next)

some earth science applications do not require this, some do

Plate Tectonics

Time Dependence

time dependence adds a third dimension to spatial data, just as the vertical dimension does

or may be added to 3 spatial dimensions to give 4D

computer science deals with time dependence of records in databases e.g., records may be valid only for limited times

Time and Geographical Data

geographical cases are more complex - objects may have limited existence, but

may also move, change shape, and change attributes

once again, set of database models for time dependent data have not been fully developed

very few temporal GISs on the market

Temporal Models: 1 - Shapes of Objects Change

shapes of objects change through time

define a limited number of time "slices"

store the objects at each slice

objects may coalesce or split from one time slice to the next
e.g. kelp beds off the Oregon coast

or use a 3D space with the vertical dimension as time, populated by 3D objects (4D)

2 - Attributes Change

attributes of objects change through time

define a limited number of time "slices"

store the attributes as separate tables for each time slice

if attributes are needed between time slices, interpolate

3 - Boundaries Change

boundaries between objects change through time

boundaries may turn on and off rather than move

the system stores all boundary lines which ever existed

then reconstructs objects from the boundaries at any given time

Combining 3-D and Time

objects at each time slice, but unrelated from one time to another - layers

objects at each time slice, related or tracked from one time to another - related layers
migration studies

objects defined continuously in the time dimension - 3D objects
individual space-time travel behavior

Classic References

Bouille, F. 1976. "A Model of Scientific Data Bank and Its Applications to Geological Data," Computers and Geosciences 2: 279-291.

Carter, J.R. 1988. "Digital Representations of Topographic Surfaces: An Overview," in American Congress on Surveying and Mapping and American Society for Photogrammetry and Remote Sensing, Technical Papers 5:54-60.

Ganter, J.H. 1989. "Comparison of Representations for Complex Earth Volumes," Auto-Carto 9: Proceedings of the Ninth International Symposium on Computer-Assisted Cartography, Baltimore, MD.

Hagerstrand, T., 1970. "What about people in Regional Science?" Papers, Regional Science Association 24:7-21. Discusses the concept of space-time prisms in human spatial behavior.

Kavouras, M. and S. Masry, 1987. "An Information System for Geosciences: Design Considerations," Auto-Carto 8: Proceedings of the Eighth International Symposium on Computer-Assisted Cartography, ASPRS/ACSM, Falls Church, VA, pp. 282-291.

Langran, G., 1989. "A review of temporal database research and its use in GIS applications," International Journal of Geographical Information Systems 3(3):215-32. Can research on time dependence in databases help in representing the effects of time in GIS data?

Langran, G. and N.R. Chrisman, 1988. "A framework for temporal geographic information," Cartographica 25(3):1- 14. Discusses models for representing temporal change in GIS.

Mark, D.M. and J.A. Cebrian, 1986. "Oct-trees: A Useful Data- Structure for the Processing of Topographic and Sub- Surface Data," ACSM/ASPRS Technical Papers 1:104-113.

Raper, Jonathan. Three Dimensional Applications in GIS, Taylor and Francis, New York. A collection of papers on the developing technology of 3D GIS.

Requicha, A.A.G. 1980. "Representations for Rigid Solids: Theory, Methods and Systems," ACM Computing Surveys 12:437-464.

Turner, A.K. 1997. "What's the Difference Among 2-D, 2.5D, 3-D, and 4-D?" GIS World 10(3): 54.

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