ISPRS Congress 2000 Multidimensional Representation of Geographic Features E. Lynn Usery Research Geographer U.S. Geological Survey

ISPRS Congress 2000 Outline Introduction Objectives Background Approach –Theoretical Basis –Implementation Strategy Application – DLG-F usage Conclusions

ISPRS Congress 2000 Introduction Need for geoinformation theory –UCGIS Research Priority on “Geographic Representation”; proposed theme on ontology. –Need to handle 3 dimensions and time –Need to interface to geographic process models Climate models Growth models Biologic models Watershed/water quality models

ISPRS Congress 2000 Introduction Geographic reality consists of entities and processes We represent entities as objects and processes as models –Mathematical (process) –Data driven (map, spatial, or GIS) –Combinations

ISPRS Congress 2000 Objectives Advance development of theory of geographic information supporting multiple representations. Validate theory in multiple applications. Develop implementation around specific application for feasibility testing. Use current GIScience knowledge as base from which to extend representation ideas.

ISPRS Congress 2000 Background Significant work toward a theory –Peuquet, 1988; Molenaar, 1991; Mark, 1993; Usery, 1996; Frank, –Geography Place, attribute, time as fundamental basis for spatial analysis from Berry (1964), basis of current GIS Region theory –Cartography Abstraction and generalization concepts

ISPRS Congress 2000 Background Cognitive psychology –Basic level of categorization exists –For geography, that level is geographic entities or features Roads Streams Buildings Watersheds …

ISPRS Congress 2000 Problems How to advance theory of geoinformation? Limits of commercial GIS software systems –Map model of reality –Geometry (raster or vector) based objects with attached attributes Needs to advance – , ,Z,t or X,Y,Z,t coordinates for entities –Motion and process

ISPRS Congress 2000 Feature Approach Feature is geographic entity and object representation One feature, many objects –Multiple resolutions –Multiple geometries –Access from single identity

ISPRS Congress 2000 Definitions

ISPRS Congress 2000

Requirements to Move from Theoretical Concepts to Implementation Theory of sufficient completeness to support application needs Transition framework from theoretical concepts to a data model Implementation methodology from the data model

ISPRS Congress 2000 Theoretical Completeness Components of theory available –Feature concepts –Human understanding Category theory Metaphor Algebraic formalisms Missing links –Feature to feature relations Some work on topological relations –Thematic, temporal relations

ISPRS Congress 2000 Transition Framework Dimensions Concepts Data Models Data Structures

ISPRS Congress 2000

Implementation Methodology Feature processing system –Create, select, manipulate, analyze features –Use existing databases Spatial, thematic, temporal attributes and relationships Vector geometry ( , ,Z,t lists) Raster geometry (pixel matrices) –Heuristics, procedures, models

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Application of the Framework Watershed/water quality modeling application Test site in Little River, Georgia, USA –340 sq. km. –Traditional data layers Soils, land cover, elevation, precipitation –Derived information Slope, aspect, flow directions, flow paths, flow planes –Multiple geometries and resolutions Vector Raster at 3, 30, 60, 120, 210, 240, 480, 960, 1920 m cells

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Implementation of Watershed Features Use USGS DLG-F structures Apply to raster geometry Build attributes and relations specific to defined features Develop parameters for water models

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Conclusions Conceptual framework (addition to theory) supporting multiple geometries and multidimensional representation developed. Geographic feature is unique entity;basis of theory –Feature has multiple object representations Transition framework from concepts to data model developed Data model to data structure transition developed

ISPRS Congress 2000 Conclusions Framework being implemented for watershed/water quality modeling Features developed Data structures for features developed from USGS DLG-F and are being implemented against raster geometry.