RadxBeamBlock

RadxBeamBlock estimates the amount of beam blockage due to terrain near a radar.

Overview

Overall, RadxBeamBlock takes elevation data, the radar location, and radar characteristics to estimate how much blockage occurs due to terrain.

Prerequesites

The following items are required:

• Digital elevation model data
• Radar antenna location
• Radar characteristics
• Parameter files for RadxBeamBlock

Digital elevation model data

Note: a NASA Earthdata account is needed to download topography data. Creating an account is free and quick to do, and can be done here.

The supported digital elevation models include Shuttle Radar Topography Mission (SRTM) and ESRI grid data (spheroid). SRTM data can be found online here. SRTM data for the entire globe is 22GB and can be a lot to download! If you only need a subsection for your region of interest, use a recursive script to download them. If you only need a few files, this is easy enough to do manually. Remember to unzip your files. Once completed, you should have a directory with .hgt files spanning your region.

Example:
 1 #!/bin/bash
 2 
 3 # download SRTM data for Taiwan region
 4 
 5 for lat in `seq 19 25`
 6   do
 7     for lon in `seq 117 123`
 8       do
 9       # get files
10       wget --user=$USERNAME --password=$PASSWORD https://e4ftl01.cr.usgs.gov/MEASURES/SRTMGL1.003/2000.02.11/N${lat}E${lon}.SRTMGL1.hgt.zip
11   done
12 done

Radar location and characteristics

The radar location requires the latitude, longitude, and elevation of the antenna (ground level + radar height). In addition, characteristics including the wavelength, beamwidth, gate spacing, azimuths, and elevation angles are required. This information can be found using RadxPrint on a raw radar file or converted radar CfRadial file.

RadxPrint -f /path/to/radar/file

Parameter files

RadxBeamBlock uses one parameter file. Compared to other Radx applications, the RadxBeamBlock parameter file requires just a few edits in order to run. Most of the parameters that need to be changed relate to the radar characteristics.

1) Main parameter file

Ensure file is up to date

To obtain the default parameter file, use the following command:

/path/to/lrose/install/bin/RadxBeamBlock -print_params > param_file_name

If you already have a parameter file and simply want to check for (and add) updated parameters while retaining current parameters, use the following command:

/path/to/lrose/install/bin/RadxBeamBlock -params orig_param_file_name -print_params > new_param_file_name

Important parameters

Input params

• input_dem_parth: directory containing the elevation data
• input_data_format: specifies the format of the elevation data (examples provided in the parameter file)

Radar parameters

• radar_location: latitude, longitude, and elevation (ground elevation
  • radar height in km) of the radar antenna
• radar_wavelength_cm: radar wavelength (cm)
• horiz_beam_width_deg: horizontal beamwidth (degrees)
• vert_beam_width_deg: horizontal beamwidth (degrees)
• gates: starting distance, gate spacing (km), and number of gates
• azimuths: starting azimuth, azimuth spacing (degrees), and number of azimuths
• elevations: starting elevation angle, angle spacing (degrees), and number of elevation angles

Output directory and file name

• output_dir: files will be written to this directory
• output_format: select the preferred file type (usually CFRADIAL)

Running RadxBeamBlock

To check all command line options for RadxBeamBlock, including debugging options and file paths, type the following command into a terminal.

/path/to/lrose/install/bin/RadxBeamBlock -h

Once your parameter file is complete, use a command similar to the following to run the application:

/path/to/lrose/install/bin/RadxBeamBlock -params param_file_name