GIS 1110

Designing Geodatabases

Representation

Q. How will we model our real world data?

A. Typically: Features Continuous Surfaces and Imagery Map Graphics

Features

Points Points in Space

i.e. Latitude and Longitude Lines

Connected points i.e. Start and End Point of a Wall May be a Set of Lines

Polygons Connected Points to Form a Shape

i.e. A Parcel of Land

Continuous Surfaces and Imagery

Triangulated Irregular Networks (TIN) A Representation of a Surface as a Set of

Triangles Can Be Useful for 3D Data

Each Triangles Can Common Elevation Points

Raster Images Pixelated (Digitized) Analog Data

Each Pixel is a Section of the Image Binary - Entire Section Has the Same

Attributes

Thematic Layers

Logical Partitioning of Map Data Into Layers Photographic (Orthophotographic)

i.e. Aerial or Satellite Photos Parcel Lines or Sections – A Grid

i.e. Quadrangles Ownership and Tax Boundaries

i.e Plot Maps Land/Site Use or Restrictions

i.e Commercial and Residential Areas Municipal/Administrative Areas

i.e. County Lines

Thematic Layers

Each Layer Is Independent Layers are Spatially Oriented So They Can

Be Overlaid Need a Common Scale Need Common Reference Points

Layers May Be Represented Differently Elevation Map – Raster or Polygons Aerial Photo – Raster Roads (Centerline) – Lines County Lines - Polygons

Feature Class

Collections of Features With A Common Representation i.e. Tax Parcels as Polygons

Features May Share a Common Boundary Line i.e. Some Parcels Touch

Often Have Integrity Rules – Constraints i.e Parcels Can Not Overlap

Feature Datasets

Collections of Feature Classes Classes Typically Have Some Relationship

i.e. A Road and a Parcel Share Some Common Points

Topologies and Networks

A Topology Defines How Features Share Geometry – How They Relate Integrity Rules

i.e. Can Not Overlap

A Network Defines Connection and Flow Between Features Connection Between Power Poles

Image Data

Raster Data - Binary, Discrete Units Not easily Scalable

Vector Data – Point Data For a Curve Readily Scalable

Vector and Raster Data Not Easily Relatable Can Convert Vector to Raster Raster to Vector Much More Difficult

Raster Datasets

Collections of Image Data Stored in Tables A Catalog Can Be One or More Tables

Which Indicate What Images Are and Where They Are Located.

Steps to Designing a Geodatabase

Three Phases or Parts Conceptual Design Logical Design Physical Design

Conceptual Design

1. Identify the Products to be Produced An Application - Reports, Forms, Web pages

2. Identify the Thematic Layers How Used, Data Sources, Scales, Symbology, etc.

3. Specify the Scale and Representation How are Layers to Interact

4. Group Representations Into Datasets Determine Feature Datasets, Rules, Domains

Logical Design

5. Define Tabular Structure Identify Fields, Ranges, Subtypes

From ERD or Normalization

6. Define Spatial Properties for the Datasets Use Networks to Enforce Spatial Integrity

and Shared Geometry 7. Propose the Design

Decide on an Overall Design

Physical Design

8. Implement, Prototype, Review and Refine Build and Load Tables, Examine and Refine

Structure and Constraints 9. Design the Work Flows for Building and

Maintaining Each Layer Design a Control Mechanism to Maintain the Data

and Its Integrity 10. Document the Design

Produce Formal Drawings, Diagrams, Dictionaries