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GIS Tutorial 1

GIS Tutorial 1. Lecture 6 Digitizing. Outline. Digitizing overview GIS features Digitizing features Advanced digitizing tools Spatial adjustments Digitizing sources. Lecture 6. Digitizing overview. Why digitize?. New maps Map features are wrong Missing features Other?.

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GIS Tutorial 1

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  1. GIS Tutorial 1 Lecture 6 Digitizing

  2. Outline • Digitizing overview • GIS features • Digitizing features • Advanced digitizing tools • Spatial adjustments • Digitizing sources GIS TUTORIAL 1 - Basic Workbook

  3. Lecture 6 Digitizing overview GIS TUTORIAL 1 - Basic Workbook

  4. Why digitize? • New maps • Map features are wrong • Missing features • Other? GIS TUTORIAL 1 - Basic Workbook

  5. Heads down digitizing • Digitizing tablets • Used to digitize hard copy maps into GIS • Transform wire intersections into coordinates of the tablet’s coordinate system GIS TUTORIAL 1 - Basic Workbook

  6. Steps for heads down digitizing • Tape map to the digitizer • Register control points on the map • Estimate two conversion equations (one for vertical and one for horizontal coordinates) • Digitize vectors (points, lines, or polygons) Tape Control points Puck Map GIS TUTORIAL 1 - Basic Workbook 6

  7. Heads up digitizing • Mouse on a screen • Digitizes paper maps, aerial photos, or other images GIS TUTORIAL 1 - Basic Workbook 7

  8. Lecture 6 Gis features GIS TUTORIAL 1 - Basic Workbook

  9. Points • Single features • Nodes • Line endpoints • Vertex points • Controls shapes of linesand polygons GIS TUTORIAL 1 - Basic Workbook

  10. Creating points • Heads up digitizing • Single point features • Sketch tool and snapping features • Points added as XY event files • Points geocoded using addresses GIS TUTORIAL 1 - Basic Workbook

  11. Lines • Starting and ending points with shape vertices as needed Vertex points GIS TUTORIAL 1 - Basic Workbook

  12. Lines • Physical attributes of TIGER streets • Shape • From and To attributes • Node • Address • Lat/long • Length GIS TUTORIAL 1 - Basic Workbook

  13. 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 0 0 GIS TUTORIAL 1 - Basic Workbook

  14. Polygons • Physical attributes • Shape • Area • Perimeter • Length GIS TUTORIAL 1 - Basic Workbook

  15. Lecture 6 Digitizing features GIS TUTORIAL 1 - Basic Workbook

  16. Create new feature class • Created in ArcCatalog GIS TUTORIAL 1 - Basic Workbook

  17. Create new feature class • Add spatial reference information GIS TUTORIAL 1 - Basic Workbook

  18. Create new feature class • Add new fields GIS TUTORIAL 1 - Basic Workbook

  19. Create new feature class • Feature class created GIS TUTORIAL 1 - Basic Workbook

  20. Creating Feature Layers or Shapefiles in ArcMap • Within ArcMap: • Locate an existing data layer that is similar to the layer that you wish to create. • Start editing the existing layer, then digitize the new feature • Select the new feature • Export the selection to a shapefile • Add the shapefile- fields already present and map projection • is already defined • Examples in the instructor exercise GIS TUTORIAL 1 - Basic Workbook

  21. Digitize new features • Create base map • Add feature in ArcMap • Start editing (Editor toolbar) • Digitize feature • Stop editing and save GIS TUTORIAL 1 - Basic Workbook

  22. Create base map for digitizing • Vector features or raster images GIS TUTORIAL 1 - Basic Workbook

  23. Add new feature class GIS TUTORIAL 1 - Basic Workbook

  24. Add Editor toolbar • Customize, Toolbars, Editor toolbar GIS TUTORIAL 1 - Basic Workbook

  25. Start editing • Editor, Start editing GIS TUTORIAL 1 - Basic Workbook

  26. Begin digitizing GIS TUTORIAL 1 - Basic Workbook

  27. Click point (tree) locations GIS TUTORIAL 1 - Basic Workbook

  28. Stop editing • Editor, Stop editing GIS TUTORIAL 1 - Basic Workbook

  29. Edit attribute data • Start editing, populate fields in table 1 2 GIS TUTORIAL 1 - Basic Workbook

  30. Lecture 6 Advanced Digitizing tools GIS TUTORIAL 1 - Basic Workbook

  31. Specify angle and length • Lines and polygons • Straight segment tool • Type length and angle GIS TUTORIAL 1 - Basic Workbook

  32. Snapping tools Point Snapping • Snapping toolbar Endpoint Snapping Vertex Snapping Edge Snapping GIS TUTORIAL 1 - Basic Workbook

  33. Trace tool • Good for complicated shapes • Editor toolbar, Trace tool GIS TUTORIAL 1 - Basic Workbook

  34. Generalize tool • Creates features for use at small scales with less detail while preserving basic shapes • U.S. Census cartographic boundary files Census TIGER water feature City planning rivers GIS TUTORIAL 1 - Basic Workbook

  35. Smooth tool • Smoothes sharp angles in polygon outlines to improve aesthetic or cartographic quality Smooth before Smooth after GIS TUTORIAL 1 - Basic Workbook

  36. Cut polygons • Creates two polygons from one original • Cut polygon tool Polygon before Polygon after GIS TUTORIAL 1 - Basic Workbook

  37. Lecture 6 Spatial adjustments GIS TUTORIAL 1 - Basic Workbook

  38. Transforms • Converts data • from one coordinate system to another. • from digitizer or scanner units to real world coordinates. • Shifts data • within a coordinate system, (e.g. feet to meters). GIS TUTORIAL 1 - Basic Workbook

  39. Rubbersheeting • Geometric distortions commonly occur in source maps • may be introduced by imperfect registration in map compilation • lack of geodetic control in source data • variety of other causes • Corrects flaws through the geometric adjustment of coordinates GIS TUTORIAL 1 - Basic Workbook

  40. Edgematching • Aligns features along the edge of one layer to features of an adjoining layer • 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. GIS TUTORIAL 1 - Basic Workbook

  41. Spatial adjustment example • Hamburg Hall CAD Drawing • CAD drawings generally do not have geographic coordinates GIS TUTORIAL 1 - Basic Workbook

  42. Spatial adjustment example • Spatially match drawing to map using displacement links GIS TUTORIAL 1 - Basic Workbook

  43. Lecture 6 Digitizing sources GIS TUTORIAL 1 - Basic Workbook

  44. USGS • United States Geological Survey • Common Data Types & Standards • Digital Elevation Models (DEMs) • Digital Orthophoto Quads(DOQQs) • Digital Line Graphs(DLGs) • Digital Raster Graphics (DRGs) • Landsat Satellite Images • Land Use Land Cover (LULC) • Spatial Data Transfer Standard(SDTS) GIS TUTORIAL 1 - Basic Workbook

  45. Orthophotography • Digital imagery in which distortion from the camera angle and topography have been removed, thus equalizing the distances represented on the image GIS TUTORIAL 1 - Basic Workbook

  46. Digital Ortho Quarter Quads—DOQQs • http://online.wr.usgs.gov/ngpo/doq/ • Grayscale or color-infrared (CIR) images • 1-meter ground resolution; • Cover an area measuring 3.75 minutes longitude by 3.75 minutes latitude, approximately 5 miles on each side • Referenced to the North American Datum of 1983 (NAD83) and cast on the Universal Transverse Mercator (UTM) projection GIS TUTORIAL 1 - Basic Workbook

  47. DOQQ image resolutions • The ground length of one pixel of the image • image with one meter resolution means that each pixel in the image represents one square meter on the ground. 30 meters 10 meters 5 meters GIS TUTORIAL 1 - Basic Workbook

  48. DOQQ image resolutions 2 meters 1 meter GIS TUTORIAL 1 - Basic Workbook

  49. National Elevation Data Sets • United States Geological Survey (USGS) National Elevation Dataset (NED) Shaded Relief Imagery Data (Free) • Maps provide highest-resolution elevation data available across the United States, in raster format • http://ned.usgs.gov/ GIS TUTORIAL 1 - Basic Workbook

  50. Scanning paper documents • Raster to vector conversion • Paper (historic) maps • Scanned maps and images become vectors • Special software needed GIS TUTORIAL 1 - Basic Workbook

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