Raster Data Analysis

• Raster data


  • Well-suited for surface- and field-related phenomena (e.g. elevation, gravity, rainfall, etc.)
  • Wide availability of datasets; all remotely sensed data of this sort
• Where rasters come from

  • Converted vector files, e.g. shapefiles, coverages
  • Directly from raster sources: remotely sensed data, DEMs, meteorological measurements, etc
• Analyses


  • Basic geoprocessing with rasters
  • Single layer analysis
  • Multiple layer analysis
  • Local, neighborhood, zonal, global
  • Surface analysis
• Single layer operations


  • Reclassification
  • Buffering
• Multiple layer operations


  • Clip
  • Raster overlay
  • Mathematical raster overlay
  • Boolean raster overlay
  • Relational raster overlay
• Reclassification


  Assigning a new class or range value to all pixels in the dataset based on their original values
• Reclassification examples


  • Binary masking
  • Weighting
• Buffering


  Creating an output dataset that contains a zone (or zones) of a specified width around an input feature
• Clip


  Overlaying a raster dataset with a vector polygon clip layer to produce a single raster that is identical to the input raster but shares the extent of the polygon clip layer
• Raster overlay


  Overlaying multiple raster datasets, requiring that all overlain rasters are covering identical areas and maintaining equal resolution (i.e. cell size)
• Map algebra


  Algebraic operations with raster layers, including arithmetic, boolean, and relational
• Map algebra examples


  • Arithmetic raster overlay
  • Boolean raster overlay
  • Relational raster overlay
• Surface


  A raster dataset that contains an attribute value for every locale throughout its extent
• Terrain mapping


  Interpolation to estimate the value of a variable at an unsampled location from measurements made at nearby or neighboring locales

  
• TIN interpolation


  Creating a surface formed by triangles of nearest neighbor points
• Raster-based overlay is preferred for projects that involve a number of layers and a considerable amount of computation
• Vector-based overlay operation can combine multiple attributes from each input layer, whereas raster in a local operation is associated with a single set of cell values
• Vector-based buffering operation creates more accurate buffer zones than a raster-based one
• Vector-based buffering operation has more flexibility in creating and manipulating separate distance measures compared to raster-based one
• Network


  A system of linear features that has the appropriate attributes for the flow of objects, typically topology-based with links (edges/arcs) and nodes (junctions)
• Traveling salesman problem

  A routing problem stipulating the salesman must visit each of the select shops only once, and the salesman may start from any stop but return to the original stop
• Vehicle routing problem


  An extension of the traveling salesman problem, finding the optimal set of routes for a fleet of vehicles to traverse in order to deliver to a given set of customers
• Shortest path analysis

  Finds the path with the minimum cumulative impedance between nodes on a network
• Closest facility analysis

  Finds the closest facility among candidate facilities to any location on a network
• Finding coverage

  Creating drive-time areas that correspond to the distance that can be reached within a specific amount of time