Spatial Data Formats

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Spatial Data Formats. Stages of development:. Conceptual model : select the features of reality to be modeled and decide what entities will represent them Spatial data model : select a format that will represent the model entities - PowerPoint PPT Presentation

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  • Spatial Data Formats

    CS 128/ES 228 - Lecture 4b

  • Stages of development:Conceptual model: select the features of reality to be modeled and decide what entities will represent them Spatial data model: select a format that will represent the model entities Spatial data structure: decide how to code the entities in the models data files

    CS 128/ES 228 - Lecture 4b

  • 2. Spatial data modelsRaster

    Vector Object-orientedSpatial data formats:

    CS 128/ES 228 - Lecture 4b

  • Raster formatFeatures represented by cell contents Spatial precision limited by cell size Surfaces modeled as continuous values

    CS 128/ES 228 - Lecture 4b

  • Vector formatSpatial precision limited by number format Discrete features explicitly represented Surfaces shown by contours rather than continuous values

    CS 128/ES 228 - Lecture 4b

  • Object-oriented formats Leave details for Dr. Levine!

    CS 128/ES 228 - Lecture 4b

  • Thematic data (a.k.a. attribute data)Quantitative or descriptive May represent 1 or many themes Tied to a spatial reference Represented differently in raster vs. vector formats

    CS 128/ES 228 - Lecture 4b

  • Scales of measurementHeywood et. al. 1998 Table 2.1

    CS 128/ES 228 - Lecture 4b

  • Spatial modeling in raster formatBasic entity is the cell Region represented by a tiling of cells Cell size = resolution Attribute data linked to individual cells

    CS 128/ES 228 - Lecture 4b

  • TesselationA closed shape or polygon that repeats on all sides without any gaps or overlaps Three regular polygons tesselate the plane:SquareEquilateral triangle Hexagon

    CS 128/ES 228 - Lecture 4b

  • TilingsIn 1922 Escher visited the Alhambra palace and saw the wall tilings of the Moors. He was excited to find other artists who had been captivated by tilings, but also made this revealing comment: "What a pity their religion forbade them to make graven images."

    CS 128/ES 228 - Lecture 4b

  • Eschers tesselations

    CS 128/ES 228 - Lecture 4b

  • Raster model close up

    CS 128/ES 228 - Lecture 4b

  • Advantages of raster formatmany data sets available different file formats readily inter-converted fast computer lookup and display easy to overlay multiple themes able to represent multiple continuous surfaces

    CS 128/ES 228 - Lecture 4b

  • Limitations of raster formatpoor representation of discrete objects constant resolution throughout region modeled exact boundary location difficultnetwork analysis nearly impossible difficult to change projection or coordinate system

    CS 128/ES 228 - Lecture 4b