Radar Clutter

This topic describes how to specify radar clutter in STK. There are two parts to modeling clutter. The first is the geometry (via a scattering point provider) for determining the location and area of clutter patches, which scatter energy back to the radar object. The second part is the clutter map (via a scattering point model) that specifies the radar cross section of each clutter patch.

To define the radar clutter for your scenario,

Open a radar object's properties.
Select the Basic > Definition page.
Select the Clutter tab.

When you select the Enabled check box, you can then specify the geometry and clutter map.

Scattering Point Provider List

If you click the ellipsis, you will see all provider lists available to you. STK defaults to one list, and this list defaults to having one provider (Single Point). You can build lists and save them to the Component Browser using the Save As New Component icon.

When you select a list, the gray box shows all the providers in the selected list.

Select the Enable check box for an individual provider to include it in the clutter configuration.
Click Add to add another provider to the currently selected list. The new provider defaults to the Single Point type, which you can change using the options in Point Provider Details section of the Clutter tab.
Click Duplicate to make an exact copy of a provider.
Click Remove to delete a provider.

When you select a provider on the list, that provider is highlighted and you can then go to the Point Provider Details section of the Clutter tab to change the Scattering Point Provider type or the Scattering Point Model type or both.

Point Provider Details

For each scattering point provider listed, you can select the geometry specifications and clutter map type for each.

Scattering Point Provider

Click the ellipsis to choose one of the following options for specifying the geometry:

Option	Description
Points File	When you select this option, you can then click the Filename ellipsis to browse to and select a points file. For a description and example, see Points file. When you select this option, you can then select a Default Scattering Point Model. STK will apply this model to all points in the file that do not have a model specified.
Python	Click under the Value column to browse to and select a file. There is an example Python Clutter Geometry plugin file in your install folder at C:/Program Files/AGI/STK12/CodeSamples/CodeSamples.zip/Extend/Radar/ClutterGeometry/Python. For more information on Python plugins in STK, see STK's Built-in Python Plugins section of the STK Python API Programmer's Guide.
Range Over CFAR Cells.	Use this option with CA-CFAR and OS-CFAR algorithms. This allows the number of CFAR reference cells, specified on the Radar->Mode->Probability of Detection tab, to be spread evenly before and after the cell of interest. Clutter is evaluated along the current scan radial before and after the cell containing the target of interest. It uses the Number of Reference cells value, provided on the Probability of Detection tab. It considers half of the number of cells before and half of the number cells after the cell of interest. For example, if the number of reference cells is 32, then the 16 cells before and the 16 cells after the current cell of interest are evaluated for clutter. The current cell of interest is the cell where Probability of Detection is being computed. AGI recommends this option for use with the Cell Averaging Constant False Alarm Rate (CA-CFAR) option or the Ordered Statistics Constant False Alarm Rate (OS-CFAR) option on the Probability of Detection tab.
Single Point	Computes a single clutter point.
Smooth Oblate Earth	Computes scattering points based on isoDoppler and isorange contours projected onto the smooth oblate model of Earth.

Scattering Point Model

Choose a model (clutter map) for determining the radar cross section of clutter patches from the following options:

Option	Description
Constant Coefficient	Specify a constant clutter coefficient value, and STK multiplies this value by the Scattering Point Provider area to determine the radar cross section.
Python	Click under the Value column to browse to and select a file. There is an example Python Clutter Map plugin file in your install folder at C:/Program Files/AGI/STK12/CodeSamples/CodeSamples.zip/Extend/Radar/ClutterMap/Python. For more information on Python plugins in STK, see STK's Built-in Python Plugins section of the STK Python API Programmer's Guide.
Wind Turbine	When you select this option, you must provide the following wind turbine modeling dimensions: Blade Length Blade Rotation (angular rate) Wind Direction (clockwise from north) Blade Scattering Cross Section Structure Scattering Cross Section

Option

Description

Constant Coefficient

Specify a constant clutter coefficient value, and STK multiplies this value by the Scattering Point Provider area to determine the radar cross section.

Python

Click under the Value column to browse to and select a file. There is an example Python Clutter Map plugin file in your install folder at C:/Program Files/AGI/STK12/CodeSamples/CodeSamples.zip/Extend/Radar/ClutterMap/Python. For more information on Python plugins in STK, see STK's Built-in Python Plugins section of the STK Python API Programmer's Guide.

Wind Turbine

When you select this option, you must provide the following wind turbine modeling dimensions:

Blade Length
Blade Rotation (angular rate)
Wind Direction (clockwise from north)
Blade Scattering Cross Section
Structure Scattering Cross Section

Using a COM plugin

A COM plugin is especially useful for dynamic modeling. If you have a scattering points provider COM plugin on your computer and you properly registered it, the plugin appears as an option when you click the Scattering Points Provider ellipsis. You can then select and enable it. If you have a Scattering Points Model (clutter map) COM plugin on your computer and you properly registered it, the plugin will appear as an option when you click the Scattering Points Model ellipsis.

The STK installation contains examples in C++, C#, Python, and WSC for the following:

Scattering Point Provider (Clutter geometry); go to C:/Program Files/AGI/STK 12/ CodeSamples/CodeSamples.zip/Extend/Radar/ClutterGeometry
Scattering Point Model (Clutter map): go to C:/Program Files/AGI/STK 12/ CodeSamples/CodeSamples.zip/Extend/Radar/ClutterMap

For more information on COM plugins, see the web links Plugin Points for COM-based Engine Plugins and Engine Plugin Registration.

Points file

A points file needs to have a *.spf file extension. The first line on the file must be exactly this:

   ScatteringPointProviderPointsFile v1

so that STK will identify and parse it properly. The second line must be exactly this:

   DataFormatType LatLonAlt

The following lines are data points of latitude, longitude, and altitude, in that order, with white space between them. You must enter latitude and longitude in degrees and altitude in meters. The optional fourth "slot" in a data line is the name of the scattering point model associated with that individual provider data point. If the name has spaces, you must either use quotes around the name or convert the spaces to underscores. If you do not provide a name, STK will apply the default scattering point model that you select on the Clutter tab.

Each line can end with a comment. Anything after a # character in the line is considered commentary.

The following is an example file:

   ScatteringPointProviderPointsFile v1
   DataFormatType LatLonAlt
   1.0 1.0 5.0 Constant_Coefficient #Name with no spaces
   1.1 1.1 15.0 #using the default clutter map
   1.2 1.2 25.0 "Wind Turbine" #Name with a space in quotes