Multidimensional Representation of Geographic Features

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, 1998. • 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

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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 ISPRS Congress 2000

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 ISPRS Congress 2000

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 ISPRS Congress 2000

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. ISPRS Congress 2000

Multidimensional Representation of Geographic Features

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