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Spatial Data Model: Basic Data Types

Spatial Data Model: Basic Data Types. 2 basic spatial data models exist vector : based on geometry of points lines Polygons raster : based on geometry of grid cells (images, bitmaps, DEMs). Vector Data. Vector Data Model. Points : represent discrete point features.

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Spatial Data Model: Basic Data Types

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  1. Spatial Data Model: Basic Data Types 2 basic spatial data models exist vector: based on geometry of • points • lines • Polygons raster: based on geometry of • grid cells (images, bitmaps, DEMs)

  2. Vector Data

  3. Vector Data Model Points: represent discrete point features each point locationhas a record in thetable airports are point features each point is stored as a coordinate pair

  4. roads are linear features Vector Data Model Lines: represent linear features each road segmenthas a record in thetable

  5. vertex vertex vertex vertex Vector Data Model node node • Lines start and end at nodes • line #1 goes from node #2 to node #1 • Vertices determine shape of line • Nodes and vertices are stored as coordinate pairs

  6. Vector Data Model Polygons: represent bounded areas each bounded polygonhas a record in thetable landforms and water are polygonal features

  7. Vector Data Model Points are discreet Nodes Vertices Lines Nodes Vertices Arcs Closed area (Lines + points ) = polygons

  8. Vector Data Model Vector data formats available in ArcGIS ESRI GeoDatabases ESRI shapefiles ArcInfo coverages and libraries CAD files (AutoCAD DWG, DXF; microstation DGN) StreetMap files Spatial Database Engine (SDE) data ASCII point coordinate data Linear measure (route) data

  9. Vector Data Model ESRI Geodatabases Geodatabase can store many files from many source formats 1st preferred vector format in ArcGIS Rapid display Fully editable (coordinate and tabular) in ArcGIS Convenient storage format Data sets are either point or line or polygon

  10. Vector Data Model ESRI shapefiles 2nd preferred vector format in ArcGIS Rapid display Fully editable (coordinate and tabular) in ArcGIS Simple in structure • Do not use arc-node topology • “Connected” lines do not necessarily share a common node • Adjacent polygons do not share common bounding arcs Data sets are either point or line or polygon

  11. Vector Data Model Shapefile polygon spatial data model • less complex data model • polygons do not share bounding lines

  12. Vector Data Model ArcInfo coverages Commonly found format (due to ArcInfo market dominance) Data model more complex Display more slowly in ArcGIS Coordinate data not editable in ArcGIS Polymorphic (point/line/polygon/route/annotation/…) Problematic OS file structure

  13. Vector Data Model ArcInfo coverage spatial data model • polygons share bounding lines • same topological rules can be built into Geodatabase

  14. Vector Data Model ASCII coordinate data Easy to obtain from a variety of sources • GPS • Traverse (survey) • Direct reading OS and application independent

  15. Vector Data Model Characteristics + Features are positioned accurately + Shape of features can be represented correctly + Features are represented discretely (no fuzzy boundaries) – Not good for representing spatially continuous phenomena – Potentially complex data structure (especially for polygons); - can lead to long processing time for analytical operations

  16. Raster Data

  17. Raster Data Model origin is set explicitly cell size is always known cell references (row/column locations)are known cell values are referencedto row/column location values represent numerical phenomena orindex codes for non-numerical phenomena

  18. digital orthophoto Raster Data Model A few different types of raster data • digital elevation model (DEM)

  19. Raster Data Model Characteristics: Rectangular grid of square cells – Shape of discrete polygonal features generalized by cells + Continuous (surface) data represented easily + Simple data structure

  20. Raster Data Model Good at representing continuous phenomena, e.g., Wind speed Elevation, slope, aspect Chemical concentration Likelihood of existence of a certain species Electromagnetic reflectance (photographic or satellite imagery)

  21. Ecological Applications: Vol. 17, No. 2, pp. 508–526. LINKING OCCURRENCE AND FITNESS TO PERSISTENCE: HABITAT-BASED APPROACH FOR ENDANGERED GREATER SAGE-GROUSE Cameron L. Aldridge and Mark S. Boyce

  22. Well_dst 10m cont. distance to nearest standing energy well Rd_dst 10m cont. distance to nearest road SB 10m cont. % sagebrush cover determined from a.p. Crop_dst 10m cont. distance to nearest cultivated land pCrop 10m cont. prop. of crop in a 1-km moving window

  23. Homework Read “getting data into ArcGIS Maps”, “displaying layers”, “changing layer display properties”, “project and data management”, “sample data”, “data export” Assignment 2. “Introduction to GIS” (due January 22)

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