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Spatial Data Models

Spatial Data Models. What do you see out the window?. Naïve view : a blur of colors on my retina Topological view : a collection of points, lines & areas in geometric relation to each other Object-oriented view : sidewalks, buildings, trees, people … Western NY view : a lot of snow.

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Spatial Data Models

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  1. Spatial Data Models CS 128/ES 228 - Lecture 4a

  2. What do you see out the window? • Naïve view: a blur of colors on my retina • Topological view: a collection of points, lines & areas in geometric relation to each other • Object-oriented view: sidewalks, buildings, trees, people … • Western NY view: a lot of snow CS 128/ES 228 - Lecture 4a

  3. What is a spatial model? A simplified representation of part of the real world, referenced to spatial coordinates, and created for a specific purpose CS 128/ES 228 - Lecture 4a

  4. Two types of features (“entities”) Discrete Continuous CS 128/ES 228 - Lecture 4a

  5. What are data? • Observations or measurements of the real world • Three “modes” (or 3 questions to answer): • Spatial mode (where is it?) • Thematic mode (what is it?) • Temporal mode (when was it observed?) CS 128/ES 228 - Lecture 4a

  6. Model dimensionality: 2-D • X-Y coordinates • No elevations • Road crossings… CS 128/ES 228 - Lecture 4a

  7. Model dimensionality: 3-D • X-Y-Z coordinates • False relief http://earth.esa.int/pub/INSAR/dem/ves_dem.gif CS 128/ES 228 - Lecture 4a

  8. More sophisticated 3-D models • Wire frame model“draped” withaerial photographor other surfacefeature • Thematic material can be layered on http://biology.usgs.gov/stt/SNT/noframe/cl111.htm CS 128/ES 228 - Lecture 4a

  9. Model dimensionality: 4-D • X-Y-Z coordinates + temporal dimension Fig. 7. A geographic information system representation of glacier shrinkage from 1850 to 1993 in Glacier National Park. The Blackfeet­ Jackson glaciers are in the center. The yellow areas reflect the current area of each glacier; other colors represent the extent of the glaciers at various times in the past.Courtesy C. Key, USGS and R. Menicke, National Park Service http://biology.usgs.gov/stt/SNT/noframe/cl111.htm CS 128/ES 228 - Lecture 4a

  10. Stages of development: • Conceptual model: select the features of reality to be modeled and decide what entities will represent them. Driven by purpose of model. • Spatial data model: select a format that will represent the model entities. Driven by conceptual model and by data availability. • Spatial data structure: decide how to code the entities in the model’s data files. CS concern. CS 128/ES 228 - Lecture 4a

  11. The modeling process • Conceptual model • Spatial datamodel CS 128/ES 228 - Lecture 4a

  12. Our local “Happy Valley” CS 128/ES 228 - Lecture 4a

  13. 1. Conceptual models • Decide the model’s purpose • Select the features to be modeled CS 128/ES 228 - Lecture 4a

  14. Spatial entities: 5 types • Points • Lines • Areas (polygons) • Networks • Surfaces CS 128/ES 228 - Lecture 4a

  15. Happy Valley spatial entities CS 128/ES 228 - Lecture 4a

  16. Points Lines Areas Networks Discrete features: Continuous features: Discrete vs. continuous features • Surfaces CS 128/ES 228 - Lecture 4a

  17. Networks • Line entity • Used to model features along which material, energy, or information flow • Special components: nodes, stops, turns, direction, impedance CS 128/ES 228 - Lecture 4a

  18. Impedance CS 128/ES 228 - Lecture 4a

  19. Surfaces • Models entity as a continuous feature • Every location has a value, even if only interpolated from discrete samples Both: http://snobear.colorado.edu/Markw/Research/ESRI/ESRI.html CS 128/ES 228 - Lecture 4a

  20. Digital terrain models CS 128/ES 228 - Lecture 4a

  21. Precision agriculture Aerial photograph Soil pH Crop yield CS 128/ES 228 - Lecture 4a

  22. Oceanography Estimate of phytoplankton distribution in the surface ocean: global composite image of surface chlorophyll a concentration (mg m-3) estimated from SeaWiFS data (Source: NASA Goddard Space Flight Center, Maryland, USA and ORBIMAGE, Virginia, USA). CS 128/ES 228 - Lecture 4a

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