# Presentation: 922580

## Multidimensional Representation of Geographic Features

- E. Lynn Usery
- Research Geographer
- U.S. Geological Survey

## Outline

- Introduction
- Objectives
- Background
- Approach
- Theoretical Basis
- Implementation Strategy
- Application – DLG-F usage
- Conclusions

## 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

## 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

## 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.

## 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

## Background

- Cognitive psychology
- Basic level of categorization exists
- For geography, that level is geographic entities or features
- Roads
- Streams
- Buildings
- Watersheds
- ...

## 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

## Feature Approach

- Feature is geographic entity and object representation
- One feature, many objects
- Multiple resolutions
- Multiple geometries
- Access from single identity

## Definitions

## Slide 11

## 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

## 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

## Transition Framework

- Dimensions
- Concepts
- Data Models
- Data Structures

## 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

## Slide 17

## 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

## 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.