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Spatial Data Entry Heywood (GIC) Chapter 5
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Learning Objectives c) Describe Spatial Data Input i.List and explain methods for entering spatial data (coordinates) into the GIS: digitizing, scanning, Global Positioning Systems (GPS), conversion software, survey instruments ii.Data formats: shapefiles, geodatabases, grids, GeoTIFF… etc. iii.Explain methods for correcting geospatial data (topology verification, edgematching, transforming, projecting)
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Spatial Data Entry Step 1: Database Design Document Step 2: Find Data Step 3: Input data into the computer Step 4: Spatial data editing and manipulation Step 5: Spatial data model verification
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Step 1: Database Design Document Spatial Data layers
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Step 2: Find Data Be careful…. Quality, screen shots vs. real data Examples –City of Vancouver Open Data site –BC government Open Data site
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Step 3: Input data Data Conversion File Transfer (Web data) –BC TRIM data (maps BC)
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GPS
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Theodolite Surveying
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Digitizing Points Lines polygons
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Air Photo On screen digitizing
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Scanning
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Keyboard Entry
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Step 4: Spatial Data Editing and Manipulation a.topology verification b.project / transform c.edgematching d.rubber sheeting / geo-referencing
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a) Topology verification: errors Undershoots overshoots duplicate labels No labels Pseudo nodes
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a) Topology verification: fixed Extend Undershoot clip overshoots delete duplicate labels Add label Delete Pseudo nodes
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b) Project Transform Project from one projection to another –Albers Equal area to Lambert Conformal Transform –digitizing coordinates to real world coordinates, –NAD27-NAD8
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c) Edgematching
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d) Geo-referencing (rubber sheeting) Taking historic airphoto and accurate city streets: making them fit
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Step 5: Spatial Data Verified
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Midterm: Short answer, 50 minutes Labs 1, 2 Lectures up to here Textbook chapters 1, 2, 3, 5 –Except: Chapter 2: –p 31- 34 before Topology –Box 2.6, 2.8, 2.9, 2.10 Chapter 3 –Box 3.5, –building computer worlds on p.64-p.68 Generally, terms and concepts that we did not cover in class
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