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Digitizing Overview

Digitizing Overview. Why Digitize?. New maps Map features are wrong Missing features. Copyright– Kristen S. Kurland, Carnegie Mellon University. Heads Down Digitizing. Digitizing table or tablet . Copyright– Kristen S. Kurland, Carnegie Mellon University. Heads Up Digitizing.

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Digitizing Overview

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  1. Digitizing Overview

  2. Why Digitize? • New maps • Map features are wrong • Missing features Copyright– Kristen S. Kurland, Carnegie Mellon University

  3. Heads Down Digitizing • Digitizing table or tablet Copyright– Kristen S. Kurland, Carnegie Mellon University

  4. Heads Up Digitizing • Mouse on a screen • Digitizes paper maps, aerial photos, or other images Copyright– Kristen S. Kurland, Carnegie Mellon University

  5. GIS Features

  6. Points • Single features • Nodes • Line endpoints • Vertex points • Controls shapes of linesand polygons

  7. Creating points • Heads up digitizing • Single point features • Sketch tool and snapping features • Points added as XY event files • Points geocoded using addresses(chapter 7)

  8. Lines • Starting and ending points with shape vertices as needed • Vertex points

  9. Lines • Physical attributes of TIGER streets • Shape • From and To attributes • Node • Address • Lat/long • Length

  10. Polygons • Three or more lines joined to form a closed area • Single polygons or multipart features • (Hawaiian islands can be multiple polygons as one feature) 4 3 1 2

  11. Polygons • Physical attributes • Shape • Area • Perimeter • Length

  12. Digitizing Features

  13. Create new feature class

  14. Create new feature class • Add spatial reference information

  15. Create new feature class • Add new fields

  16. Create new feature class

  17. Digitize new features • 1.Create base map • 2. Add feature in ArcMap • 3. Start editing (Editor toolbar) • 4. Digitize feature • 5. Stop editing and save

  18. Create base map for digitizing • Vector features or raster images

  19. Add new feature class

  20. Add Editor toolbar • Customize, Toolbars, Editor toolbar

  21. Start editing • Editor, Start editing

  22. Begin digitizing

  23. Click point (tree) locations

  24. Stop editing • Editor, Stop editing

  25. Edit attribute data • Start editing, populate fields in table

  26. Advanced Tools

  27. Specify angle and length • Lines and polygons • Straight segment tool • Type length and angle

  28. Snapping tools • Snapping toolbar

  29. Trace tool • Good for complicated shapes • Editor toolbar, Trace tool

  30. Generalize tool • Creates features for use at small scales with less detail while preserving basic shapes • U.S. Census cartographic boundary files • City planning • rivers • Census TIGER water feature

  31. Smooth tool • Smoothes sharp angles in polygon outlines to improve aesthetic or cartographic quality • Smooth before • Smooth after

  32. Cut polygons • Creates two polygons from one original • Cut polygon tool • Polygon before • Polygon after

  33. Spatial Adjustments

  34. Spatial Adjustments • Transform • Rubbersheet • Edgematch Copyright– Kristen S. Kurland, Carnegie Mellon University

  35. Transforms • Convert data from one coordinate system to another. • Converts data from digitizer or scanner units to real world coordinates. • Shifts data within a coordinate system, such as converting feet to meters. Copyright– Kristen S. Kurland, Carnegie Mellon University

  36. Rubbersheeting • Geometric distortions commonly occur in source maps. • They may be introduced by imperfect registration in map compilation, lack of geodetic control in source data, or a variety of other causes. • Rubbersheeting corrects flaws through the geometric adjustment of coordinates. Copyright– Kristen S. Kurland, Carnegie Mellon University

  37. Edgematching • The edgematching process aligns features along the edge of one layer to features of an adjoining layer. • The layer with the less accurate features is adjusted, while the adjoining layer is used as the control. • Attribute transfer is typically used to copy attributes from a less accurate layer to a more accurate one. Copyright– Kristen S. Kurland, Carnegie Mellon University

  38. Spatial Adjustment Example • Hamburg Hall Building Drawn in CAD • Spatially Adjusted to Aerial Photo Copyright– Kristen S. Kurland, Carnegie Mellon University

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