Download Geographic Information Systems - CEProfs

Map Analysis with
Raster Datasets
Francisco Olivera, Ph.D., P.E.
Department of Civil Engineering
Texas A&M University
Map Query
Map Query is a local function that
creates a grid with cell values 1
(true), 0 (false) or NODATA
depending on the outcome of a
condition.
The condition can involve one or
more grids.
To query grids, click on
Analysis/Map Query…
DEM < 100
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
cells, make the themes active, and click
on Analysis/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,
make the grid active, and click on
Analysis/Neighborhood Statistics…
Mean over a 5-cell-radius circular neighborhood
Summarize Zones
Summarize Zones 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.
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
Analysis/Summarize Zones…
Histograms by Zones
Histogram by Zone is a zonal
function that creates a column chart
of histograms of the cell values
within each zone.
The zones can be defined by
polygons or (integer) grid cells with
the same value.
To create the zone histograms, click
on Analysis/Histograms by Zones…
Tabulate Areas
Tabulate Areas is a zonal function
which creates a table that stores
the area of the common areas of
zones defined by two themes of
zones.
The zones can be defined by
polygons or (integer) grid cells with
the same value.
To create the zone histograms, click
on Analysis/Tabulate Areas.
Find Distance
Find Distance is a global
function which creates a grid
that stores the Euclidean
distance from the cell to the
closest feature or nonNODATA cell.
To find the distance, click on
Analysis/Find Distance.
Assign Proximity
Assign Proximity is a global
function which creates a grid
that stores the identification
number of the closest feature
or non-NODATA cell.
To assign proximity, click on
Analysis/Assign Proximity.
Interpolate grid
Interpolate grid is a global
function which creates a grid
that stores values interpolated
from a point feature dataset.
To interpolate a grid, click on
Surface/Interpolate Grid.
Create Contours
Create contours creates a line
feature dataset in which the
lines connect points of equal
cell value.
To create contours, click on
Surface/Create contours.
Derive Slope
Derive 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.
Derive slope does not indicate
the direction of the calculated
slope.
To derive the slope, click on
Surface/Derive Slope.
Derive Aspect
Derive 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 derive the slope, click on
Surface/Derive Aspect.
Compute Hillshade
Compute 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 derive the slope, click on
Surface/Compute Hillshade.
Line Profile
Line Profile creates a chart and
dbf table of grid values vs.
distance along selected features
of the line theme.
Merges selected features of the
line theme, finds points at equal
intervals (user is queried for
number of divisions of merged
line), and queries grid theme for
cell values at points. .
To derive the slope, click on
CRWR-Raster/Line Profile
Raster Data Development
Mosaic creates a grid out of a set of grids. In non-overlapping zones, the output
grid cells are assign the value of the input grid. In overlapping zones, smooth
transitions are calculated. Output grid cells are assign NODATA wherever all
input grids have NODATA cells. To mosaic grids, click on CRWR-Raster/Mosaic.
Merge creates a grid out of a set of grids. In non-overlapping zones, the output
grid cells are assign the value of the input grid. In overlapping zones, the output
grid cells take the value from the input grids according to their priority. Input
grids are given a priority when calling the Merge function. NODATA cells in input
grids are ignored. Output grid cells are assign NODATA wherever all input grids
have NODATA cells. To merge grids, click on CRWR-Raster/Merge.
Resample changes the cell size of a grid by interpolation. No new data is
generated. To resample grids, click on CRWR-Raster/Resample.
Raster Data Development
Clip Grid by Graphic creates a grid in
which the cell values are equal to the
input grid inside the selected graphic,
and NODATA outside.
To clip grids by graphics, click on
CRWR-Raster/Clip Grid by Graphic.
Raster Data Development
Clip Grid by Polygons creates a grid in
which the cell values are equal to the
input grid inside the selected polygons
of the feature dataset, and NODATA
outside.
To clip grids by polygons, click on
CRWR-Raster/Clip Grid by Polygons.