Spatial Data Entry Heywood (GIC) Chapter 5

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)

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

Step 1: Database Design Document Spatial Data layers

Step 2: Find Data Be careful…. Quality, screen shots vs. real data Examples –City of Vancouver Open Data site –BC government Open Data site

Step 3: Input data Data Conversion File Transfer (Web data) –BC TRIM data (maps BC)

GPS

Theodolite Surveying

Digitizing Points Lines polygons

Air Photo On screen digitizing

Scanning

Keyboard Entry

Step 4: Spatial Data Editing and Manipulation a.topology verification b.project / transform c.edgematching d.rubber sheeting / geo-referencing

a) Topology verification: errors Undershoots overshoots duplicate labels No labels Pseudo nodes

a) Topology verification: fixed Extend Undershoot clip overshoots delete duplicate labels Add label Delete Pseudo nodes

b) Project Transform Project from one projection to another –Albers Equal area to Lambert Conformal Transform –digitizing coordinates to real world coordinates, –NAD27-NAD8

c) Edgematching

d) Geo-referencing (rubber sheeting) Taking historic airphoto and accurate city streets: making them fit

Step 5: Spatial Data Verified

Midterm: Short answer, 50 minutes Labs 1, 2 Lectures up to here Textbook chapters 1, 2, 3, 5 –Except: Chapter 2: –p 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