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