Transcript Spatial Analysis with Raster Datasets - 2 - CEProfs

Spatial Analysis with
Raster Datasets - 2
Francisco Olivera, Ph.D., P.E.
Srikanth Koka
Department of Civil Engineering
Texas A&M University
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.
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.
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.
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, cheapest 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.
Calculation = 0.34*Reclass of
landUse + 0.66* Reclass of
Slope
Density
Density can be used to
create a continuous density
surface from a set of input
features within the search
area.
The options for creating a
density grid are Simple
density or Kernel density.
To create a density
surface, click on Spatial
Analyst/Density.
Density surface of population data
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.
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.
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 3–cell
neighborhood.
Slope does not indicate the
direction of the calculated slope.
To create a slope surface, click on
Spatial Analyst/Surface
Analysis/Slope.
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.
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.
Surface Analysis-Viewshed
Viewshed is a global
function which creates a
grid of visible and nonvisible surface from an
observation point.
To create a viewshed grid,
click on Spatial Analyst/
Surface Analysis/
Viewshed.
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.
Only in ArcGIS 8.3
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…
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 5-cell-radius circular neighborhood
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…
Raster Calculator
The Raster Calculator is
a calculator that
evaluates local functions.
To query grids, click on
Spatial Analyst/Raster
Calculator…
DEM < 100
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