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, 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

Feature - A set of phenomena with common attributes and relationships. The concept of feature encompasses both entity and object.

Entity - A real-world phenomenon that cannot be subdivided into phenomena of the samekind.

Object - A digital representation of all or a part of an entity.

Attribute - Characteristic of a feature or of an attribute value.

Relationship - Linkage between features or objects.

Feature instance - An occurrence of a feature defined by a unique set of attributes andrelationships.

Definitions

ISPRS Congress 2000

Dimensions, Attributes, and Relationships of Geographic Phenomena

Space Theme Time-----------------------------------------------------------------------------------------------------------Attributes φ,λ,Z color, size, date, duration

point, line, area, shape, ph, ... period, ...surface, volume, pixel, voxel, ...

-----------------------------------------------------------------------------------------------------------Relationships topology, topology, topology,

direction, is_a, kind_of, is_a, was_a,distance, ... part_of, ... will_be ...

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

Feature

Dimensions Space Theme Time

Concepts Image Schemata Experiential Continuous flowLanguage Formal Time slicesMetaphor Category theory Dynamic events

Data Models Geometry Relations RelationsTopology Objects Predictive formulas

Data Structures Vector lis ts Tables TablesRaster matrices Frames EquationsArc/node tables Semantic nets Semantic nets

Features Knowledgebase

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

User Interface

Feature ListFeature Processors

Feature Feature Feature Feature Manipulation Creator Selector Analyzer

Databases

Feature

Heuristics,Procedures,Models

Spatial Thematic Temporal φ,λ,Z,t lists Attributes and Relationships Pixel matrices

Image and map store

Features Knowledgebase

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

Watershed Features Modeled from Raster Geometry

Entity Object Attributes Relationships------------------------------------------------------------------------------------------------------Gaging station Pixel Table of heights Subwatershed area

Sampling station Pixel Table of wq values Subwatershed areaStream Line of pixels Name Connects to: streams

Table of flow Flow from: flowplanesFlowplane Pixel Slope (avg) Flows to: stream

aggregationSubwatershed Pixel Area Composed of: flowplanes

Aggregation Contains: streamPart of: subwatershed

ISPRS Congress 2000

Feature Attributes Relationships

Watershed

Spatial attributes Spatial RelationshipsBounding coordinates Adjacent watershedsPour point Containing watersheds

Contained watersheds

Thematic Attributes Thematic RelationshipsElevation (DEM matrix) Composed of subwatershedsSlope (Raster matrix) Contains drainage networkAspect (Raster matrix)Land cover (Raster matrix)Soils (Raster matrix)Name

Temporal Attributes Temporal RelationshipsDate State compared to time tn

ISPRS Congress 2000

Feature Attributes Relationships

Sampling station

Spatial attributes Spatial relationshipsX,Y,Z location Pour point for watershed

Pour point for sampling stations ...

Thematic attributes Thematic RelationshipsWater volume Date/TimeChemical content (time tn)

PhPNH4

Biotic content (time tn)E. Coli

Name

Temporal attributes Temporal relationshipsDate Time of thematic values

ISPRS Congress 2000

Feature Attributes Relationships

Flow plane

Spatial attributes Spatial RelationshipsBounding coordinates Opposite flowplanePour point Bounding stream

Bounding ridgeContaining flowplanesContained flowplanes

Thematic Attributes Thematic RelationshipsElevation (DEM matrix) Composed of subwatershedsSlope (Raster matrix) Contains drainage networkAspect (Raster matrix)Land cover (Raster matrix)Soils (Raster matrix)Name

ISPRS Congress 2000

Feature Attributes Relationships

Drainage network

Spatial attributes Spatial RelationshipsCenterline coordinates Flows intoPour point Containing watersheds

Contained watersheds

Thematic AttributesName

ISPRS Congress 2000

Feature Attributes Relationships

Stream

Spatial attributes Spatial RelationshipsCenterline coordinates Part of networkPour point Flows from

Flows to

Thematic AttributesName

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

ISPRS Congress 2000

ISPRS Congress 2000

ISPRS Congress 2000

ISPRS Congress 2000

ISPRS Congress 2000

ISPRS Congress 2000

ISPRS Congress 2000

ISPRS Congress 2000

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.