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Kernel, Line and Point Density

Husam Jubeh
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Kernel,  Line and Point Density Tools

Kernel Density

How to use Kernel Density Tool in Arc Toolbox??

Kernel Density Tool
Kernel Density

Path to access the tool

:

Kernel Density Tool, Density Toolset, Spatial Analyst Tools Toolbox

 

Kernel Density

Calculates a magnitude-per-unit area from point or polyline features using a kernel function to fit a smoothly tapered surface to each point or polyline.



1. Input point or polyline features

The input features (point or line) for which to calculate the density.

2. Population field

Field denoting population values for each feature. The population field is the count or quantity to be spread across the landscape to create a continuous surface.

Values in the population field may be integer or floating point.

The options and default behaviors for the field are listed below.

  1. Use None if no item or special value will be used and each feature will be counted once.
  2. You can use Shape if input features contains Z.
  3. Otherwise, the default field is POPULATION. The following conditions may also apply.
  • If there is no POPULATION field, but there is a POPULATIONxxxx field, this is used by default. The xxxx can be any valid character, such as POPULATION6, POPULATION1974, or POPULATIONROADTYPE.
  • If there is no POPULATION field or POPULATIONxxxx field, but there is a POP field, this is used by default.
  • If there is no POPULATION field, POPULATIONxxxx field, or POP field, but there is a POPxxxx field, this is used by default.
  • If there is no POPULATION field, POPULATIONxxxx field, POP field, or POPxxxx field, NONE is used by default.

3. Output raster

The output kernel density raster.

It is always a floating point raster.

4. Output cell size (optional)

The cell size of the output raster that will be created.

This parameter can be defined by a numeric value or obtained from an existing raster dataset. If the cell size hasn't been explicitly specified as the parameter value, the environment cell size value will be used if specified; otherwise, additional rules will be used to calculate it from the other inputs. See the usage for more detail.

5. Search radius (optional)

The search radius within which to calculate density. Units are based on the linear unit of the projection of the output spatial reference.

For example, if the units are in meters—to include all features within a one-mile neighborhood—set the search radius equal to 1609.344 (1 mile = 1609.344 meters).

The default search radius (bandwidth) is computed specifically to the input dataset using a spatial variant of Silverman's Rule of Thumb that is robust to spatial outliers (that is, points that are far away from the rest of the points). See the usage tips above for a description of the algorithm.

6. Area units (optional)

The desired area units of the output density values.

A default unit is selected based on the linear unit of the output spatial reference. You can change this to the appropriate unit if you wish to convert the density output. Values for line density convert the units of both length and area.

If no output spatial reference is specified, the output spatial reference will be the same as the input feature class. The default output density units is determined by the linear units of the output spatial reference as follows. If the output linear units are meters, the output area density units will be set to SQUARE_KILOMETERS, outputting square kilometers for point features or kilometers per square kilometers for polyline features. If the output linear units are feet, the output area density units will be set to SQUARE_MILES.

If the output units is anything other than feet or meters, the output area density units will be set to SQUARE_MAP_UNITS. That is, the output density units will be the square of the linear units of the output spatial reference. For example, if the output linear units is centimeters, the output area density units will be SQUARE_MAP_UNITS, which would result in square centimeters. If the output linear units is kilometers, the output area density units will be SQUARE_MAP_UNITS, which would result in square kilometers.

The available options and their corresponding output density units are the following:

  1. SQUARE_MAP_UNITS—For the square of the linear units of the output spatial reference.
  2. SQUARE_MILES—For miles (U.S.).
  3. SQUARE_KILOMETERS—For kilometers.
  4. ACRES—For acres (U.S.).
  5.  HECTARES—For hectares.
  6. SQUARE_YARDS—For yards (U.S.).
  7. SQUARE_FEET—For feet (U.S.).
  8. SQUARE_INCHES—For inches (U.S.).
  9. SQUARE_METERS—For meters.
  10. SQUARE_CENTIMETERS—For centimeters.
  11. SQUARE_MILLIMETERS—For millimeters

7. Output values are (optional)

Determines what the values in the output raster represent.

  1. DENSITIES—The output values represent the predicted density value. This is the default.
  2. EXPECTED_COUNTS—The output values represent the predicted amount of the phenomenon within each cell.Since the cell value is linked to the specified cell size, the resulting raster cannot be resampled to a different cell size and still represent the amount of the phenomenon.

8. Method (optional)

Determines whether to use a shortest path on a spheroid (geodesic) or a flat earth (planar) method. It is strongly suggested to use the geodesic method with data stored in a coordinate system that is not appropriate for distance measurements (for example, Web Mercator or any geographic coordinate system) and any analysis that spans a large geographic area.

  1. PLANAR—Uses planar distances between the features. This is the default.
  2. GEODESIC—Uses geodesic distances between features. This method takes into account the curvature of the spheroid and correctly deals with data near the poles and the International dateline.

Line Density

How to use Line Density Tool in Arc Toolbox??

Line Density Tool
Line Density

Path to access the tool

:

Line Density Tool, Density Toolset, Spatial Analyst Tools Toolbox

 

Line Density

Calculates a magnitude-per-unit area from polyline features that fall within a radius around each cell.



1. Input polyline features

The input line features for which to calculate the density.

2. Population field

Numeric field denoting population values (the number of times the line should be counted) for each polyline.

Values in the population field may be integer or floating point.

The options and default behaviors for the field are listed below.

  1. Use None if no item or special value will be used and each feature will be counted once.
  2. You can use Shape if input features contains Z.
  3. Otherwise, the default field is POPULATION. The following conditions may also apply.

  • If there is no POPULATION field, but there is a POPULATIONxxxx field, this is used by default. The xxxx can be any valid character, such as POPULATION6, POPULATION1974, or POPULATIONROADTYPE.
  • If there is no POPULATION field or POPULATIONxxxx field, but there is a POP field, this is used by default.
  • If there is no POPULATION field, POPULATIONxxxx field, or POP field, but there is a POPxxxx field, this is used by default.
  • If there is no POPULATION field, POPULATIONxxxx field, POP field, or POPxxxx field, NONE is used by default.

3. Output raster

The output line density raster.

It is always a floating point raster.

4. Output cell size (optional)

The cell size of the output raster that will be created.

This parameter can be defined by a numeric value or obtained from an existing raster dataset. If the cell size hasn't been explicitly specified as the parameter value, the environment cell size value will be used if specified; otherwise, additional rules will be used to calculate it from the other inputs. See the usage for more detail.

5. Search radius (optional)

The search radius within which to calculate density. Units are based on the linear unit of the projection of the output spatial reference.

For example, if the units are in meters—to include all features within a one-mile neighborhood—set the search radius equal to 1609.344 (1 mile = 1609.344 meters).

The default is the shortest of the width or height of the output extent in the output spatial reference, divided by 30.

6. Area units (optional)

The desired area units of the output density values.

A default unit is selected based on the linear unit of the output spatial reference. You can change this to the appropriate unit if you wish to convert the density output. Values for line density convert the units of both length and area.

If no output spatial reference is specified, the output spatial reference will be the same as the input feature class. The default output density units is determined by the linear units of the output spatial reference as follows. If the output linear units are meters, the output area density units will be set to SQUARE_KILOMETERS, outputting square kilometers for point features or kilometers per square kilometers for polyline features. If the output linear units are feet, the output area density units will be set to SQUARE_MILES.

If the output units is anything other than feet or meters, the output area density units will be set to SQUARE_MAP_UNITS. That is, the output density units will be the square of the linear units of the output spatial reference. For example, if the output linear units is centimeters, the output area density units will be SQUARE_MAP_UNITS, which would result in square centimeters. If the output linear units is kilometers, the output area density units will be SQUARE_MAP_UNITS, which would result in square kilometers.

The available options and their corresponding output density units are the following:

  1. SQUARE_MAP_UNITS—For the square of the linear units of the output spatial reference.
  2. SQUARE_MILES—For miles (U.S.).
  3. SQUARE_KILOMETERS—For kilometers.
  4. ACRES—For acres (U.S.).
  5.  HECTARES—For hectares.
  6. SQUARE_YARDS—For yards (U.S.).
  7. SQUARE_FEET—For feet (U.S.).
  8. SQUARE_INCHES—For inches (U.S.).
  9. SQUARE_METERS—For meters.
  10. SQUARE_CENTIMETERS—For centimeters.
  11. SQUARE_MILLIMETERS—For millimeters

Point Density

How to use Point Density Tool in Arc Toolbox??

Point Density Tool
Point Density

Path to access the tool

:

Point Density Tool, Density Toolset, Spatial Analyst Tools Toolbox

 

Point Density

Calculates a magnitude-per-unit area from point features that fall within a neighborhood around each cell.



1. Input point features

The input point features for which to calculate the density.

2. Population field

Field denoting population values for each point. The population field is the count or quantity to be used in the calculation of a continuous surface.

Values in the population field may be integer or floating point.

The options and default behaviors for the field are listed below.

  1. Use None if no item or special value will be used and each feature will be counted once.
  2. You can use Shape if input features contains Z.
  3. Otherwise, the default field is POPULATION. The following conditions may also apply.

  • If there is no POPULATION field, but there is a POPULATIONxxxx field, this is used by default. The xxxx can be any valid character, such as POPULATION6, POPULATION1974, or POPULATIONROADTYPE.
  • If there is no POPULATION field or POPULATIONxxxx field, but there is a POP field, this is used by default.
  • If there is no POPULATION field, POPULATIONxxxx field, or POP field, but there is a POPxxxx field, this is used by default.
  • If there is no POPULATION field, POPULATIONxxxx field, POP field, or POPxxxx field, NONE is used by default.

3. Output raster

The output point density raster.

It is always a floating point raster.

4. Output cell size (optional)

The cell size of the output raster that will be created.

This parameter can be defined by a numeric value or obtained from an existing raster dataset. If the cell size hasn't been explicitly specified as the parameter value, the environment cell size value will be used if specified; otherwise, additional rules will be used to calculate it from the other inputs. See the usage for more detail.

5. Neighborhood (optional)

Dictates the shape of the area around each cell that is used to calculate the density value.

  1. Annulus—A torus (donut shaped) neighborhood defined by an inner and outer radius.
  2. Circle—A circular neighborhood with the given radius. This is default where the radius is the shortest of the width or height of the extent of the input point features, in the output spatial reference, divided by 30.
  3. Rectangle—A rectangular neighborhood with the given height and width.
  4. Wedge—A wedge-shaped neighborhood. A wedge is specified by a start angle, an end angle and a radius. The wedge extends counterclockwise from the starting angle to the ending angle. Angles are specified in arithmetic degrees (counterclockwise from the positive x-axis). Negative angles may be used.
  5. Cell | Map—Defines the units of the selected neighborhood measurements in either cells or map units (based on the linear unit of the projection of the output spatial reference).

6. Area units (optional)

The desired area units of the output density values.

A default unit is selected based on the linear unit of the output spatial reference. You can change this to the appropriate unit if you wish to convert the density output. Values for line density convert the units of both length and area.

If no output spatial reference is specified, the output spatial reference will be the same as the input feature class. The default output density units is determined by the linear units of the output spatial reference as follows. If the output linear units are meters, the output area density units will be set to SQUARE_KILOMETERS, outputting square kilometers for point features or kilometers per square kilometers for polyline features. If the output linear units are feet, the output area density units will be set to SQUARE_MILES.

If the output units is anything other than feet or meters, the output area density units will be set to SQUARE_MAP_UNITS. That is, the output density units will be the square of the linear units of the output spatial reference. For example, if the output linear units is centimeters, the output area density units will be SQUARE_MAP_UNITS, which would result in square centimeters. If the output linear units is kilometers, the output area density units will be SQUARE_MAP_UNITS, which would result in square kilometers.

The available options and their corresponding output density units are the following:

  1. SQUARE_MAP_UNITS—For the square of the linear units of the output spatial reference.
  2. SQUARE_MILES—For miles (U.S.).
  3. SQUARE_KILOMETERS—For kilometers.
  4. ACRES—For acres (U.S.).
  5.  HECTARES—For hectares.
  6. SQUARE_YARDS—For yards (U.S.).
  7. SQUARE_FEET—For feet (U.S.).
  8. SQUARE_INCHES—For inches (U.S.).
  9. SQUARE_METERS—For meters.
  10. SQUARE_CENTIMETERS—For centimeters.
  11. SQUARE_MILLIMETERS—For millimeters

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