While terrain has a profound effect on the propagation of radio signals, more localized features of the environment, such as trees, buildings and houses, can also have a substantial impact. At higher frequencies using shorter paths, signal propagation may be dominated by local obstructions rather than by terrain, making Land Use (Clutter) data an important component of signal studies. Urban and residential structures can reflect, scatter and absorb radio waves. In forested land, the signal can also be weakened due to scattering of radio waves by leaves and branches. Land Use (Clutter) databases give you the ability to add additional losses above and beyond path loss and terrain effects.

In this knowledge base, Land Use (Clutter) is also referred to as: groundcover, land use, land use/land clutter, LULC, LUC, or simply “clutter”.

To set up LULC databases, select Databases>Land Use (Clutter) from the main menu bar. This will bring up the dialog box for selecting the Directory path of land use (clutter) database and its attendant Attenuation data file name. The Land Use (Clutter) dialog box also has options to create clutter databases from vector (polyline) data as well as to carve clutter by using a streets database to create street canyons within clutter categories. EDX software supports four types of clutter data formats:

• EDX .GCE format – the EDX CirrusTM clutter file format is only for use with EDX SignalPro

• EDX .GCV format – the current EDX default clutter file format

• USGS-EDX Format (.151 files) – this is a legacy format and not used much

• MSI Planet land use (clutter) data format

Regardless of which database format Type selected, in the Directory path field, specify the disk drive and directory where the data is stored. 

Like the “EDX universal .201 format” terrain type, the “EDX .GCV format” clutter type allows mixing files of varying data resolution within the same data directory. The files are automatically sorted by the program so if two or more files overlap a geographic point, the file with the best (smallest point spacing) resolution will be used for the terrain elevation of that point.

Once the clutter database path is set, in the Attenuation data file name field, you’ll need to enter the name and location of the clutter attenuation file associated with this data. Attenuation files provide the link between the raw numbers of the clutter data file, and what they represent. For example, the clutter data file may have numbers ranging from 1-10, with each number representing a clutter type; i.e. 1 for water, 2 for forest, 3 for suburban, etc.

EDX provides a number of default attenuation files designed to work with specific clutter data sets. They are located in the \data directory of the software install directory and will have in the name some form of “GCATTN” or “atten”, and end with the “.dat” extension.

Once you have configured the clutter directory and attenuation file, Click OK back to the main map to activate your clutter database. If you’re changing an existing Directory path or Attenuation data file name, you may see the following dialog box:

If you have already run studies, this gives you the option to keep those results until you’re ready to re-run the study, or to just delete the study files and start again.

Edit Attenuation File

When you click on the Edit attenuation file button, a dialog box opens listing clutter code, label and clutter height in the top half of the screen, and frequencies and attenuation values in the lower half.

Clutter Codes, Labels and Heights

A maximum of 100 land use or clutter categories can be included in the database. Clutter code numbers must fall within the range of 0 to 99 (0 = null or "no clutter"); they do not need to be numbered sequentially. Each code number corresponds to a given name and, if desired, a height value (in meters).

To add a clutter category entry use the Add entry button on the right of the dialog box. A blank highlighted line will appear. To assign code, label and height to the new category entry, place the cursor in the respective boxes in the Edit entry section of the dialog box. To modify an existing category entry, highlight that entry and go to the Edit entry section. To delete a category entry, highlight it, and then click the Delete entry button. 

Height values can be used to further refine your signal study and system configuration by showing where potential obstacles are located. Height values are used when the propagation model options Add clutter height to terrain height or Add clutter pass-through loss are selected in the Propagation Models dialog box (Studies>Propagation Models). This is most helpful in urban areas, where blockage is caused by buildings and structures, or in areas where the signal will be passing over or through a forested region. If you are working in a small city you might assign the “dense urban” category a height of perhaps 15 meters. However, that same category has a greater average height in a major metro area. You do not need to assign a height value to all the clutter categories; you can simply enter 0. For some categories, such as open ground and water, this is the appropriate value.

Loss from Clutter at Receiver

This table works with the Add Clutter Loss selection in the Propagation Models dialog box. When the EDX software runs the study calculations, at each study point it performs a lookup in the clutter data file, and if there is a clutter type at that location, does a lookup on this table to find the clutter code, and interpolating to the closest frequency entry, adds a direct loss at that point. For example, in the above dialog box, clutter code 7 shows 17dB of loss at 450mHz. So, if our study point is in that type of clutter, we would add 17dB of loss to that point. 

You can set the attenuation values for a maximum of 25 frequencies for each clutter category. These values may be theoretically or empirically based. To set the values, go to the bottom half of the dialog box and highlight the desired clutter code. To edit the frequencies, click on the Edit frequencies button. You may also add or delete frequencies here.  When done, click OK. To set the attenuation values for each clutter code at a particular frequency, highlight a clutter code and click on the Edit Attenuations button. Highlight a frequency, then go to the bottom of the Edit Attenuations dialog box and type in the value, then click OK to return to the Edit Land Use (Clutter) Attenuation File dialog box. When you have completed your changes, click the Save file and close button.

Once the clutter database information has been correctly entered, the data is available for use. You can display a map of clutter information or you can elect to use clutter information for your propagation study where path loss values can be refined by clutter loss information.

Pass Through Clutter Loss

Instead of using a fixed attenuation value at the receiver to accommodate clutter losses, you can assign a pass-through attenuation factor to the various clutter types. This tab works with the Add clutter pass-through Loss selection in the Propagation Models dialog box. When running the study, the program will determine the distance that the signal passes through a clutter type based upon the radio path profile and the clutter height values. The dB/KM attenuation values can be edited in the same way as described above. 

Create Land Use (clutter) Data-file

Returning to the Land Use (Clutter) dialog box, there are times when the clutter database you’re using may not reflect the current state of land use in your study area. A common example is if your clutter database shows an area as being forest but that forest has been cut down and converted to suburban housing units. It’s not practical to modify the “.gcv” clutter files to reflect the change. Instead, you can use the Create land use (clutter) datafile feature to make a new file that covers that converted area.

Start by using the Land Use (Clutter) Region draw tool selection from the Draw menu. Select the desired Land Use (Clutter) Type from the menu and click OK to save and close the dialog box, then draw the polygon around the area, and save it to a file. Browse to and select the file in the Name of BNA file with clutter region data field. Then in the Directory/filename for new clutter datafile field, Browse to and select a location for the output conversion file. Finally, set your Grid spacing (if you want 30 meters, enter 1 arc second) and then click the Create land use (clutter) file button. If you haven’t already done so, you can then move the newly-created “.gcv” file to your land use database directory path. 

To use the new data once you’ve converted the “.bna” and copied the “.gcv” file into your land use database directory path, save your project, exit the EDX Software then restart it and re-open your project. If you’ve displayed the land use on the screen, you’ll need to either reset all the working files, or change your study grid spacing by a slight amount to delete the existing display file and force a re-draw of the main map.

Modify Existing Ground-cover Database

Clutter carving (available only in EDX SignalPro) is a unique feature that allows taking clutter data of medium resolution and adding a “streets/roads” type of land use category by using a streets/roads database to define where the roadways are. One can imagine the process as that of a street or road route being used to “carve” a path through the clutter types found in the original file. This process is quite useful where high resolution clutter data, that already includes streets/roads, is not readily available or is unreasonably high in cost.

To carve or modify a clutter database, the source clutter data must be in the EDX GCV format. It is important to note that when clutter carving is performed, it needs to be done one GCV file at a time. To start the process, click the Carve clutter button to open the Create Carved Clutter Dialog box. The source “.GCV” file is entered in the Landuse .GCV source file field. There is also a check box option to Automatically set Land-Use/Clutter Database to use this directory which copies the directory location of the “.GCV” source file and uses it as the clutter database directory in the main program.

Once the source clutter data file is specified, you need to specify the files that define the streets and roads which will form the new clutter categories. The entry Directory for street polylines will contain the path to the directory (folder) that contains the “.BNA” files containing the polylines describing the streets/roads. These files can be created automatically from the EDX GIS database of U.S. streets. To use this option, you must first specify the location of the EDX U.S. GIS data files in the Databases>EDX Geographic Data dialog box described later.

You also must specify a Study Grid that encloses the geographic area containing the streets to be transferred to the .BNA files. The Clutter Code for Streets is used to set the code to be assigned to the new streets/roads. This can be set to 0 if you are not intending to assign attenuation values to the streets or roads.

Clicking the Create streets from EDX GIS data button will open a dialog box where you can select which street layers you want to include in the “.bna” files, as well as the effective width of each street type. Click on Create Street/Road BNA File to start the process; when it is complete click OK to return to the previous dialog box.

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To create the new clutter “.gcv” file, you first need to specify a location for the new file in the Directory for modified .GCV data field. This directory needs to be different than the directory where the source “.GCV” file is located since the new clutter file will take the same name as the original file.

Finally, before creating the new clutter file, it is important to carefully consider the value to be used for the .GCV Resolution Multiplier. This value controls the super-sampling of the original file by artificially increasing the resolution of the original data matrix. This is needed when the original file resolution is coarser than the desired street/road widths. For example, it would be difficult to resolve the location of a 15 meter wide street if the data points in a “.gcv” clutter file were set at 30 meters. In this case, better data point spacing might be 5 meters; therefore you would choose a multiplier of 6 to create a point spacing of 5 meters from the original 30-meter point spacing data. Be aware that the new clutter file will be larger in file size by a factor of the square of the multiplier value. For example, if the multiplier is 6, the new “.gcv” file will be 36 times larger than the original file and it will also take longer for the “carve” process to create the new file.

A second option that can be used to modify the source clutter file data is to reclassify the clutter data codes. This can be done as a separate function from the carving process or can be included when the carving is performed. Reclassification is the process where the clutter category for an area in the source file can be changed to a new category in the output file, by creating a polygon area that encloses the area to be changed and then specifying the new category code. Specify the directory that contains these polygon definition file(s) in Directory for land use polygon reclassification.

Import From Vertical Mapper (optional)

This is a separate option for EDX SignalPro and is installed after SignalPro is installed. If the Vertical mapper option is not installed, the Import button will not be enabled in the Land Use (Clutter) dialog box.

To initiate the Vertical Mapper “.grc” files import process, press the Import button in the Land Use (Clutter) dialog which opens the following dialog box:

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In the Source Directory path field, enter the directory location that contains the Vertical Mapper “.grc” files you want to import. Then, in the Destination Directory path field, enter the location where you want the resultant EDX “.gcv” files to be placed. Make sure that only the Vertical Mapper files you want transferred are in the Source Directory location, because EDX SignalPro will try to import all “.grc” files in that location. To start the file import process, press the Import button in the Import Vertical Mapper Clutter Dialog box.

After you have imported the Vertical Mapper files, they can be used in EDX SignalPro. To use the files, first change the Directory path in the Land Use (Clutter) dialog box to point to the “.gcv” file location. Make sure to select the “EDX .GCV format” for the Type and set the Attenuation data file name. For each imported file, a “.gcv” file is created along with an attenuation data “.dat” file. In most cases, each of the attenuation data files will contain the same information, since the Dictionary or Legend in each of the clutter files will be the same. So, choose any of those created files for the Attenuation data file name. If you want to display this new clutter, make sure you: 1) have added the “land use” map layer to the map Layers Name list in the Map Layers dialog box 2) are displaying the area where this clutter is located and 3) are defining the Study Grid within that clutter area.