Spatial Analysis with Raster Datasets 2

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Spatial Analysis with Raster Datasets - 2

• Francisco Olivera, Ph.D., P.E.
• Srikanth Koka
• Department of Civil Engineering
• Texas AM University

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Reclassification

• Reclassify creates a new grid by replacing the
  input cell values with new output cell values.
• New cell values are based on new information or
  grouping existing values together.
• To reclassify, click on Spatial
  Analyst/Reclassify.

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Straight Line Distance

• Straight Line gives the distance from each cell
  in the grid to the closest source (point or line
  dataset).
• Optionally, Create Allocation and Create
  Direction can be used to create grids with cells
  representing the value of the source and
  direction (out of eight options) of the source,
  respectively.
• To use the straight line distance function, click
  on Spatial Analyst/ Distance/Straight Line.

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Allocation

• Allocation is used to allocate cells to the
  closest source. The source can be a point feature
  class or any grid or feature class. It is similar
  to the Straight Line Allocation function.
• To create an allocation grid click on Spatial
  Analyst/ Distance/Allocation.

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Cost Weighted Distance

• The Cost Weighted Distance function creates a
  grid in which each cell represents the least
  accumulative cost from that cell to the nearest
  source (cost can be money, time, etc.).
• Needs a cost grid for example Cost raster
  f(slope, landuse).
• To create a cost weighted distance grid, click on
  Spatial Analyst/Distance/Cost Weighted.

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Interpolate to Raster

• Interpolate to raster is a global function which
  creates a grid that stores values interpolated
  from a point feature dataset.
• The options are Inverse Distance Weighted, Spline
  and Kriging.
• To create an interpolated surface, click on
  Spatial Analyst/Interpolate to Raster.

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Surface Analysis-Contour

• Create contours creates a line feature dataset in
  which the lines connect points of equal cell
  value.
• To create contours, click on Spatial
  Analyst/Surface Analysis/Contour.

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Surface Analysis-Slope

• Slope is a neighborhood function which creates a
  grid of maximum rate of change of the cell values
  of the input grid. The slope is derived based on
  a 3 x 3cell neighborhood.
• Slope does not indicate the direction of the
  calculated slope.
• To create a slope surface, click on Spatial
  Analyst/Surface Analysis/Slope.

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Surface Analysis-Aspect

• Aspect is a neighborhood function which creates a
  grid of aspect or direction of maximum slope of
  the cells of the input grid.
• Aspect values are in degrees with 0 for the
  North direction.
• To create a aspect surface, click on Spatial
  Analyst/ Surface Analysis/Aspect.

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Surface Analysis-Hillshade

• Hillshade is a neighborhood function which
  creates a grid of surface brightness for a given
  position of a light source.
• Hillshade values can be used to enhance the
  legend of themes.
• To create a hillshade surface, click on Spatial
  Analyst/Surface Analysis/ Hillshade.

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Surface Analysis-Viewshed

• Viewshed is a global function which creates a
  grid of visible and non-visible surface from an
  observation point.
• To create a viewshed grid, click on Spatial
  Analyst/ Surface Analysis/ Viewshed.

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Surface Analysis-Cut/Fill

• Cut/Fill is a local function that creates a
  surface with cells representing the area and
  volume of cut or fill needed to modify a source
  surface to a destination surface.
• To create a cut/fill surface, click on Spatial
  Analyst/Surface Analysis/Cut/Fill.

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Cell Statistics

• Cell Statistics is a local function that creates
  a grid with cell values equal to a statistic of
  the corresponding cell values of the input grids.
• The statistic can be majority, maximum, mean,
  median, minimum, minority, range, standard
  deviation, sum and variety.
• To calculate the statistics of a set of grids,
  click Spatial Analyst/Cell Statistics

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Neighborhood Statistics

• Neighborhood Statistics is a focal function that
  creates a grid with cell values equal to a
  statistic of the neighborhood cell values of the
  input grid.
• The statistic can be majority, maximum, mean,
  median, minimum, minority, range, standard
  deviation, sum and variety.
• The neighborhood can have different shapes.
• To calculate neighborhood statistics, select the
  grid and click on Spatial Analyst/Neighborhood
  Statistics

Mean over a 20-cell square neighborhood
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Zonal Statistics

• Zonal Statistics is a zonal function that creates
  a table with all the statistics of the cell
  values within each zone. Table rows correspond to
  zones and columns to statistics. This function
  can also create a chart of user-specified
  statistics.
• The statistics are majority, maximum, mean,
  median, minimum, minority, range, standard
  deviation, sum and variety.
• The zones can be defined by polygons or (integer)
  grid cells with the same value.
• To summarize by zones, click on Spatial
  Analyst/Zonal Statistics

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Raster Calculator

• The Raster Calculator is a calculator that
  evaluates local functions.

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Histogram

• The Histogram is a global function that creates a
  column chart of the cell values.
• To create a histogram, click on the Histogram
  tool.

Histogram of cell values of the reclassification
of elevation grid into 10 classes