METplus Practical Session Guide (Version 4.0) | Session 1: METplus Setup/Grid-to-Grid > MET Tool: Gen-Vx-Mask

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, 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, and the output netcdf_file must be passed on the command line.