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First Steps For Starting Your Parcel Database: Aurora Case Study. Indiana GIS Conference Dearborn County GIS Ileana Abot. Outline. Overview. Main Task - problems. different methods - comparison. Method/alternative selected. Experience/conclusions. Overview.
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First Steps For Starting Your Parcel Database:Aurora Case Study Indiana GIS Conference Dearborn County GIS Ileana Abot
Outline • Overview • Main Task - problems • different methods - comparison • Method/alternative selected • Experience/conclusions
Overview • Hired by Dearborn County in June, 2006 • help on daily requests for GIS: Maps, Data • Collaborate with County Historic Structures Project • Continue working on Aurora Zoning Map • Participate on GIS Task Force Meetings
City of Aurora • S.E. of Dearborn Co. • Incorporated community • Population: almost 4,000 ha.
Main Task • Started working on Zoning Layer • Software: Worked with ArcEditor • Existent Parcel Layer (historic district) • Edited Existent Zoning Draft • Needed more accurate data
First Problem • BOUNDARIES ??? • Lack of Parcel data
First Problem • BOUNDARIES ??? • Parcels 100 Ft. off
First Decision • Start working on Parcel Layer • assign parcel project for whole county • Select from available methods • Choose existent layers for reference • Gather all useful data (digital, maps)
Methods • Vary on Accuracy and cost • Digitize scanned maps (subdivision plats) • Use orthophotos for heads up digitizing • Include COGO descriptions: not feasible • Integrate survey data (cad): not available
Comparison of Methods Source: Designing Geodatabases: Case Studies in GIS Data Modeling, d. arctur and M. zeiler, ESRI, 2004
Parcels Database Phase 1 Phase 2 Phase 3 Collect data and line work Convert to Polygons Add Attribute Data • Development Process
Method Selected • Combined method • Vectorized Maps: Edit existent Data • Digitize scanned maps (subdivision plats) • Digitized orthophotos
Base Data • Indiana Orthophotography Project • Existent Parcel Layer (Line Work) • New Subdivision Plats • Zoning Ordinances • Knowledge provided by local authorities
Edited existing Line Work • Moving Blocks
Process Incorporate Hard - Copy Maps Scan Geo- reference Collect Data Cycle Edit & Digitize Verify
Geo-Referencing • Locate your data in real world coordinates
Geo-Referencing • All layers must be aligned (Use Control points)
Potential Errors • Accuracy of original field measurements • Scale of source map • Accuracy of original drafting • Digitizing accuracy • Conflict between different records
Process Better Accuracy USE ROW FROM STREET CENTERLINES USE SNAPPING TOOL CONSISTENT WITH SCALE
Snapping • Improves accuracy on vertices and edges junctions
Experience • City has GIS starting point • Without knowing Building Parcel Database • Trial and error process • Plan Commission Meetings: Feedback • Also located billboards and cell towers