COMPUTER CARTOGRAPHY

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COMPUTER CARTOGRAPHY
Chapter 19

• Types of Computer Maps
• Approaches to Computer Mapping
• Advantages Disadvantages

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Two Types of Computer Maps1- Raster Maps

• maps created by Cells or Pixels
• each cell location has an X and Y value
• horiz. vertical
• each cell/pixel has a data value
• e.g., elevation
• cells/pixels have a real size

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2 - Vector Maps

• Lines and Points are created by X,Y coordinates
• a Points is a single X,Y
• an X,Y points has No Size
• allows much higher levels of Precision
• a Line is comprised of Two X,Y points
• and data on how they are connected
• more attractive maps

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MAP PRECISION vs. MAP ACCURACY

• Precision How many decimal points you can have
  for a location
• Accuracy How closely the mapped object reflects
  its real world location
• Note Inkjet Plotters most popular these days
  for CAC use

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Two Approaches to Computer Mapping

• 1 - Computer Cartography
• aka Computer Assisted Cartography (CAC)
• 2 - Geographic Information Systems
• (GIS)
• BOTH
• computer based
• manipulate Points, Lines Polygons

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CAC

• manipulates Unintelligent Graphic Objects
• drawing, moving, changing the lookof Points,
  Lines Polygons
• Raster Drawing Programs
• seldom used for Cartography
• Vector Computer Aided Drafting (CAD)
• Widely used in Mechanical and Civil Engineering

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GIS

• manipulates Databases
• to draw, move, changing the look of Points,
  Lines Polygons
• Raster Remote Sensing images/photos
• resource management over large areas
• Vector Urban Planning
• and Smaller are Resource Management

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Recent Trends

• Merging CAC GIS approaches
• ESRIs ArcCAD
• Autodesks AutoCAD Map
• But, these have not been widely adopted
• Desktop Thematic Mapping
• Simplified GIS programs
• Come with Maps and some Data
• Spreadsheets, Statistical Programs, simple GIS
• Popular for Marketing studies

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Advantages of CACover Hand Cartography

• 1 - Easy to Modify existing digital base maps to
  create new maps
• 2 - Can achieve very high levels of accuracy
• 3 - Can store digital maps easier than paper maps
• 4 - Can easily adjust coordinates to their proper
  location (Geocoding)
• 5 - Can easily overlay and visually compare
  Geocoded maps to one another

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Advantages (cont.)

• 6 - Most CAC systems allow some DATA to be
  attached to the Points, Lines Polygons
• 7 - Can allow opportunities for New Presentation
  Methods
• Interactive Computer Maps
• CD ROMS, WWW, Public Kiosks
• 8 - Can Purchase ready made maps in common formats

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Disadvantages of CAC

• 1 - Initial Map Conversion (Data Capture) Cost
• Digitising
• Scanning
• Operator Assisted Scanning
• 2 - Finished results are often less attractive
  than hand-drawn maps

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Disadvantages (cont.)

• 3 - Conversion between Raster and Vector data
  formats can be difficult time consuming
• 4 - Computer software and equipment maintenance
  and upgrading Costs
• 5 - Staff Training Costs can be high
• 6 - Organisational Inertia

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SUMMARY

• Computer Cartography
• Types of Computer Maps
• Raster, Vector
• Approaches to Computer Mapping
• CAC, GIS, Desktop Thematic Mapping
• Advantages Disadvantages of Computer
  Cartography over Hand Cartography