Advanced
GIS
Using
ESRI ArcGIS 9.3
Spatial Analyst 2
Spatial Analyst
Cell Statistics
A raster will be
created depicting
the spatial
distribution of
various statistic
parameters
calculated for 2 or
more input rasters
Cell Statistics
Spatial Analyst
MAJORITY — Calculates the majority (value that occurs most often) of the inputs.
MAXIMUM — Calculates the maximum (largest value) of the inputs.
MEAN — Calculates the mean (average) of the inputs.
MEDIAN — Calculates the median of the inputs.
MINIMUM — Calculates the minimum (smallest value) of the inputs.
MINORITY — Calculates the minority (value that occurs least often) of the inputs.
RANGE — Calculates the range (difference between largest and smallest value) of the
inputs.
STD — Calculates the standard deviation of the inputs.
SUM — Calculates the sum (total of all values) of the inputs.
VARIETY — Calculates the variety (number of unique values) of the inputs.
Spatial Analyst
Cell Statistics
Example of result
Spatial Analyst
Neighborhood
Statistics
Statistical
parameters (the
same as for the
previous
command) can be
calculated for a
specified
neighborhood in a
map (point or
raster), creating a
new raster
Spatial Analyst
Neighborhood
Statistics
The neighborhood
can be defined as
a rectangle (rarely
used), giving its
size
Spatial Analyst
Neighborhood
Statistics
The neighborhood
can be defined as
a rectangle (most
used), giving its
radius
Spatial Analyst
Neighborhood
Statistics
The neighborhood
can be defined as
an annulus (similar
to a circle with lowpass filter), giving
its radiuses
Spatial Analyst
Neighborhood
Statistics
The neighborhood
can be defined as
a wedge (useful in
case of spatial
trends and/or to
highlight them),
giving its radius
and its starting and
ending directions
Spatial Analyst
Zonal Statistics
Calculates a table
of statistics (Mean,
Majority, Maximum,
Median, Minimum,
Minority, Range,
Standard
Deviation, Sum or
Variety) on values
of a raster within
the zones of
another dataset.
An histogram can
be created too for
one of the statistic
parameters.
Spatial Analyst
Zonal Statistics
Result
Spatial Analyst
Zonal Histogram
Draws a chart of
the frequency of
valus in a raster
map divided by
zones defined by a
shapefile
(generally
polygons)
Spatial Analyst
Zonal Histogram
Result
Spatial Analyst
Reclassify
Reclassifies a raster
Classes are defined
by thresholds, either
manually typed or
created with the
classify option
(identical to that
used for symbology)
Spatial Analyst
Reclassify
Result
Spatial Analyst
Convert
Feature to Raster
Creates a raster
whose cell will
contain a
value/label derived
from a field of a
shapefile.
It will cause loss of
accuracy
(frequently also
errors)
Spatial Analyst
Convert
Feature to Raster
Points
Spatial Analyst
Convert
Feature to Raster
Points
Result
Spatial Analyst
Convert
Feature to Raster
Points
Problems
All the values are
shifted to the
center of their cell
Value shifted
Spatial Analyst
Convert
Feature to Raster
Points
Problems
Since each cell can
contain only one
vaue, when two
source points are
located in the
same cell one of
them will be lost
Value lost
Spatial Analyst
Convert
Feature to Raster
Lines
Spatial Analyst
Convert
Feature to Raster
Lines
Result
Spatial Analyst
Convert
Feature to Raster
LInes
Problems
Reshaping/
simplification of
lines
“Widening” of lines
Spatial Analyst
Convert
Feature to Raster
Points
Problems
Since each cell can
contain only one
vaue, when two or
more source lines
cross the same cell
only the attribute of
one of them will be
preserved
Value lost
Spatial Analyst
Convert
Feature to Raster
Polygons
Spatial Analyst
Convert
Feature to Raster
Polygons
Result
Spatial Analyst
Convert
Feature to Raster
Polygons
Problems
Reshaping/
simplification of
polygons
Very small
polygons can be
lost
Spatial Analyst
Convert
Raster to features
Also the
conversion of
rasters to features
will generate errors
Spatial Analyst
Convert
Raster to features
to points
A shapefile of
points will be
created containing
one point for each
(non empty) cell of
the source raster
Spatial Analyst
Convert
Raster to features
to points
Result
Spatial Analyst
Convert
Raster to features
to points
Spatial Analyst
Convert
Raster to features
to points
Result
Spatial Analyst
Convert
Raster to features
to points
Spatial Analyst
Convert
Raster to features
to points
Result
Spatial Analyst
Convert
Raster to features
to points
Problems
Spatial Analyst
Convert
Raster to features
to Lines
A shapefile of
Polylines will be
created containing
lines following the
boundaries
between cells
containing different
values
Spatial Analyst
Convert
Raster to features
to points
Result
Completely
unuseful
Spatial Analyst
Convert
Raster to features
to Lines
Spatial Analyst
Convert
Raster to features
to Lines
Result
Spatial Analyst
Convert
Raster to features
to Lines
Result
Problems
Spatial Analyst
Convert
Raster to features
to lines
A raster created
from points
generally is not
accepted to
generate polylines
or polygons
Spatial Analyst
Convert
Raster to features
to Polygons
A shapefile of
Polygons will be
created following
the boundaries
between cells
containing different
values
Spatial Analyst
Convert
Raster to features
to Polygons
Result
Spatial Analyst
Convert
Raster to features
to Polygons
Result
Problems
Spatial Analyst
Convert
Raster to features
to Lines
Spatial Analyst
Convert
Raster to features
to Lines
Result
Practically unuseful
Spatial Analyst
Raster
Calculator
The Raster
Calculator can
perform
mathematical
calculations
using operators
and functions, set
up selection
queries, or type
in Map Algebra
syntax.
Inputs can be
raster datasets
(or raster layers,
coverages,
shapefiles,
tables, constants,
and numbers).
Spatial Analyst
Raster
Calculator
The most
common
functions are
represented by
icons on the
right; further
function are
available cliching
on the “expand”
button (bottom
right)
Spatial Analyst
Raster
Calculator
Expressions can
be simply typed
or created using
the selection
fields and the
function icons.
Clicking the
“Evaluate” button
a new raster will
be created
containing the
result
For example, the spatial distribution of the average
number of components of families can be avaluated
simply dividing the raster containing the interpolated value
of inhabitants per municipality by that created interpolating
the number of families per municipality
Spatial Analyst
Raster Calculator
Result
The resulting map
is always a
remporary raster
called “Calculation”
(if needed adding a
number) that can
be saved into the
HD
Spatial Analyst
Raster Calculator
Result
Extent and cell size
of the resulting
map are to be set
in the “Options”
sector of the
Spatial Analyst
Menu