spatial data entry via digitizing n.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Spatial Data Entry via Digitizing PowerPoint Presentation
Download Presentation
Spatial Data Entry via Digitizing

Loading in 2 Seconds...

play fullscreen
1 / 13

Spatial Data Entry via Digitizing - PowerPoint PPT Presentation


  • 95 Views
  • Uploaded on

Spatial Data Entry via Digitizing. Digitizing. Process of collecting digital coordinates Common data entry method Process by which coordinates from a map, image, or other sources are converted into a digital format in GIS. Digital spatial data. Data in computer compatible format Text files

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Spatial Data Entry via Digitizing' - lynne


Download Now An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
digitizing
Digitizing
  • Process of collecting digital coordinates
  • Common data entry method

Process by which coordinates from a map, image, or other sources are converted into a digital format in GIS

digital spatial data
Digital spatial data
  • Data in computer compatible format
    • Text files
    • List of coordinates
    • Digital images
    • Coordinate and attribute data in electronic file format
  • Common source of digital information
digitizing methods
Digitizing Methods
  • Manual digitization

Human guided coordinate capture from a map or image source

    • On-screen digitizing (heads-up digitizing)
    • Hard map digitizing
characteristics of manual digitizing
Characteristics of Manual Digitizing
  • Data accuracy may be affected due to
    • Equipment characteristics
    • Abilities and attitude of person digitizing
    • Map scale
      • may negatively affect the positional quality of spatial data
      • Greater for smaller scale maps
      • Effect of 1 mm on different scales
      • Table 4-1
digitizing process
Digitizing Process
  • Display image on screen
  • Trace locations of feature
    • Point
      • Features that are viewed as points
    • Line
      • linear features
      • Starting point is called ‘starting node’
      • vertices: intermediate nodes
      • Ending node
    • Polygon
digitizing errors
Digitizing Errors

Positional errors are inevitable in manual digitization

  • Undershoots and overshoots
    • Common error of digitization
    • Undershoots: nodes that do not quite reach the line or another node
      • Cause unconnected networks and unclosed polygons
    • Overshoots: lines that cross over existing nodes or lines
      • May cause difficulties in network analyses
node and line snapping
Node and Line Snapping
  • To reduce undershoots and overshoots while digitizing
  • Snapping: process of automatically setting nearby points to have the same coordinates.
    • Relies on a snap tolerance or snap distance
    • Prevent a new node from being placed within the snap distance of an already existing node – new node is joined or snapped to the existing node ensuring connection between digitized lines
reshape line smoothing and thinning
Reshape: Line Smoothing and Thinning
  • Software may provide tools to
    • Smooth
    • Densify
    • Thin
  • Spline Function
  • To smoothly interpolate curves between digitized points