METplus Practical Session Guide (Version 5.0) | Session 1: Grid-to-Grid > MET Tool: Gen-Vx-Mask

IMPORTANT NOTE: If you are returning to the tutorial, you must source the tutorial setup script before running the following instructions. If you are unsure if you have done this step, please navigate to the Verify Environment is Set Correctly page.

Gen-Vx-Mask Functionality

The Gen-Vx-Mask tool may be run to speed up the execution time of the other MET tools. Gen-Vx-Mask defines a bitmap masking region for your domain. It takes as input a gridded data file defining your domain and a second argument to define the area of interest (varies by masking type). It writes out a NetCDF file containing a bitmap for that masking region. You can run Gen-Vx-Mask iteratively, passing its output back in as input, to define more complex masking regions.

You can then use the output of Gen-Vx-Mask to define masking regions in the MET statistics tools. While those tools can read ASCII lat/lon polyline files directly, they are able to process the output of Gen-Vx-Mask much more quickly than the original polyline. The idea is to define your masking region once for your domain with Gen-Vx-Mask and apply the output many times in the MET statistics tools.

Gen-Vx-Mask Usage

View the usage statement for Gen-Vx-Mask by simply typing the following:

Usage: gen_vx_mask  
  input_file Gridded data file defining the domain
  mask_file Defines the masking region and varies by -type
  out_file Output NetCDF mask file to be written
  -type string Masking type: poly, poly_xy, box, circle, track, grid, data, solar_alt, solar_azi, lat, lon, shape
  [-input_field string] Define field from input_file for grid point initialization values, rather than 0.
  [-mask_field string] Define field from mask_file for data masking.
  [-complement, -union, -intersection, -symdiff] Set logic for combining input_field initialization values with the current mask values.
  [-thresh string] Define threshold for circle, track, data, solar_alt, solar_azi, lat, and lon masking types.
  [-height n, -width n] Define dimensions for box masking.
  [-shapeno n] Define the index of the shape for shapefile masking.
  [-value n] Output mask value to be written, rather than 1.
  [-name str] Specifies the name to be used for the mask.
  [-log file] Outputs log messages to the specified file
  [-v level] Level of logging
  [-compress level] NetCDF compression level

At a minimum, the input data_file, the input mask_poly polyline file, the output netcdf_file, and the type must be passed on the command line.