Command line executable to convert Marthe Grid file to netCDF

At the installation an executable ncmart is added to PATH and can be used to easily convert a Marthe grid file to NetCDF format.

nb: the next commands are shell commands, the ‘!’ mark is only here for the python notebook version.

# how to use: print help message
!ncmart -h

usage: ncmart [-h] [--output OUTPUT] [--variable VARIABLE] [--as2d]
              [--xyfactor XYFACTOR] [--version]
              [grid timesteps ...]

Convert a Marthe GridFile to netCDF format.

positional arguments:
  grid timesteps        Paths to grid and timesteps files are expected

options:
  -h, --help            show this help message and exit
  --output OUTPUT, -o OUTPUT
                        Output filename. Default is input.nc
  --variable VARIABLE, -v VARIABLE
                        Variable (field) to read, default is None: i.e
                        variable will be parsed from file and ONLY the first
                        variable will be read. Pass 'all' to get all
                        variables.
  --as2d, -d            Store grid as 2D (or more), default is 1D for space
                        dimension
  --xyfactor XYFACTOR, -x XYFACTOR
                        Transformation factor for coordinates. Optional,
                        default is 1 (no transformation).
  --version, -V         Show version and exit

gridmarthe  Copyright (C) 2025  BRGM.
This program comes with ABSOLUTELY NO WARRANTY.
This is free software, see GNU General Public Lisence v3 for copying.

# minimal setup: call ncmart with a grid file and a timestep file
# this will write the output with input filename and 'nc' extension
!ncmart ./data/chasim_hallue.out ./data/hallue.pastp

# print variables headers and dimensions with netcdf/nco tools
!ncdump -h ./data/chasim_hallue.nc

netcdf chasim_hallue {
dimensions:
	time = 205 ;
	zone = 927 ;
variables:
	double charge(time, zone) ;
		charge:_FillValue = NaN ;
		string charge:varname = "CHARGE" ;
		string charge:units = "m" ;
		charge:missing_value = 9999. ;
		string charge:standard_name = "water_table_level" ;
		string charge:long_name = "groundwater head" ;
	float x(zone) ;
		x:_FillValue = NaNf ;
		string x:units = "m" ;
		string x:axis = "X" ;
		string x:coverage_content_type = "coordinate" ;
	float y(zone) ;
		y:_FillValue = NaNf ;
		string y:units = "m" ;
		string y:axis = "Y" ;
		string y:coverage_content_type = "coordinate" ;
	float dx(zone) ;
		dx:_FillValue = NaNf ;
	float dy(zone) ;
		dy:_FillValue = NaNf ;
	int64 time(time) ;
		string time:units = "days since 1995-07-31 00:00:00" ;
		string time:calendar = "proleptic_gregorian" ;
	int zone(zone) ;
	int izone(zone) ;

// global attributes:
		string :conventions = "CF-1.10" ;
		string :title = "Modélisation du bassin de la SOMME Nappe_Libre" ;
		:marthe_grid_version = 9. ;
		string :original_dimensions = "x,y,z [grids]: 53 54 1" ;
		string :lon_resolution = "0.5" ;
		string :lat_resolution = "0.5" ;
		:scale_factor = 1. ;
		string :nested_grid = "False" ;
		string :extend = "xymin : 596.75 2542.25; xymax: 622.75 2568.75" ;
		string :period = "1995-2012" ;
		string :frequency = "30 day(s)" ;
		string :creation_date = "Created on 2025-12-09T15:47:09Z UTC" ;
		string :institution = "BRGM, French Geological Survey, Orléans, France" ;
		string :comment = "Hydrogeological model created with MARTHE code (Thiery, D. 2020. Guidelines for MARTHE v7.8 computer codefor hydro-systems modelling. report BRGM/RP-69660-FR)." ;
		string :resolution_units = "m" ;
		string :projection = "epsg:27572" ;
		string :domain = "FR-France" ;
}