ANALYSIS 3 - RASTER What kinds of analysis can we do with GIS?

1
ANALYSIS 3 - RASTERWhat kinds of analysis can we
do with GIS?

• Measurements
• Layer statistics
• Queries
• Buffering (vector) Proximity (raster)
• Filtering (raster)
• Map overlay (layer on layer selections)
• Transformations
• Reclassification

2
What kinds of analysis can we do with GIS?

• Network analysis
• Spatial interpolation
• Grid (raster) analysis
• Surface analysis
• Analytic modeling (Appendix)

3
Proximity map for hotels in Happy Valley (a)
distance surface (b) 125 m buffer zones
4b. Proximity - Raster

• Concentric equidistant zones established around
  a starting point
• Uses one raster layer, result is another raster
  layer where the attribute
• of each cell is a measure of distance.
• In ArcMap Spatial Analyst extension, distance,
  allocation (ArcMap refers to this as straight
  line allocation)

4
Raster GIS filter operations
5. Filtering (raster)

• Value of a cell are changed based on attribute
  values of other cells
• Example recalculating a valuefor cell c4
• Different approachesmin value, max, mean,
  modal
• Often used to smooth noisy data (e.g., seams
  between two digital elevation models)- WE WILL
  DO THIS TODAY
• For seams, in ArcMap, Spatial Analyst, Raster
  calculator, mosaic

5
6e. Raster Overlay

• Map Algebra or Mapematics (p. 268 Bolstad)
• Chapter 10 of Bolstad
• Two raster layers with same cell size
• Can add, subtract, multiply, divide them to
  produce a new layer
• In ArcMap Spatial Analyst extension, Raster
  Calculator
• We will do this today

6
Raster overlays (a) point-in-polygon (using
add) (b) line-in-polygon (using add) (c)
polygon-on-polygon (using add)
7
Raster overlays (d) polygon-on-polygon (Boolean
alternatives)
8
7. Transformations

• Raster to vector conversion
• In ArcMap, 3-D analyst extension, convert, raster
  to feature
• Vector to raster conversion
• In ArcMap, 3-D analyst extension
• Raster to Triangular Irregular Network (TIN)
• In ArcGIS, 3-D analyst extension
• Resampling a raster grid convert one cell size
  to another cell size shown on page 172 of
  coursepack

9
8. Reclassification

• Converting attribute table field values to some
  new field and values (p. 236 Bolstad)
• Example Converting a landuse layer with 21
  different landuse categories to a layer that is
  just forest (1) or no forest (0). Polygons with
  value of 10 (forest) should get a value of 1
  (yes) otherwise 0 (no).
• Example Satellite image classification
• Can be done in vector or raster
• In ArcMap
• Reclassification in ArcMap help refers to
  raster
• Vector Open table, edit, field calculator
• Raster either in Spatial analyst, reclassify
  (or using raster calculator) or in 3-D analyst

10
11a. Grid Analysis Local Functions

• Calculate output grid values based on the values
  from multiple grids at the same location (map
  calculator)
• Local statistics on two or more grid themes
• Majority, maximum, mean, median, minimum, sum,
  etc.
• In ArcMap, spatial analyst, cell statistics

11
11b. Grid Analysis Neighborhood Functions

• Can also calculate statistics on cells that are
  found within a neighborhood. Neighborhood shapes
• Rectangle
• Circle
• Doughnut
• Wedge
• Irregular
• Statistics produced
• Majority, maximum, mean, median, minimum, sum,
  etc.
• In ArcMap, spatial analyst, neighborhood
  statistics

12
12. Surface Analysis(Ch. 11 Bolstad)

• Contour
• Slope
• Aspect
• Hillshade
• Visibility analysis (Viewshed in ArcMap)
• Good table on p. 290 Bolstad on commonly
  usedterrain variables and their importance.
• In ArcMap, Spatial Analyst extension, Surface
  analysis - TODAY Also in 3-D analyst.

13
Slope over DEM
14
Ray tracing for visibility analysis
Visibility Analysis
In ArcMap 3-D Analyst, surface analysis, viewshed
15
Some ways to get data into Raster format

• They are already in a raster format (e.g.,
  Internet files)
• DEMs
• Orthophotos
• Landsat images
• ESRI Grid format
• You convert vector data to raster in Spatial
  Analyst extension
• Creates a Grid
• You create a new raster in a raster software
• ERDAS Imagine Idrissi ENVI ER Mapper
  Multispec, others