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
