GIS interoperability and export (shapefile, raster)
This notebook shows how to export gridmarthe features to common GIS format.
Script API
# import modules
import numpy as np
import gridmarthe as gm
Shapefile, step 1: conversion
gridmarthe use the geopandas API to convert grids to a geodataframe object.
path_to_data = './data'
ds = gm.load_marthe_grid(f'{path_to_data}/chasim_hallue.out', 'CHARGE', fpastp=f'{path_to_data}/hallue.pastp').isel(time=-1)
gdf = gm.to_geodataframe(ds)
gdf.head()
| charge | time | x | y | dx | dy | geometry | |
|---|---|---|---|---|---|---|---|
| zone | |||||||
| 1 | 9999.0 | 2012-07-01 | 596.75 | 2568.75 | 0.5 | 0.5 | POLYGON ((596.5 2568.5, 597 2568.5, 597 2569, ... |
| 2 | 9999.0 | 2012-07-01 | 597.25 | 2568.75 | 0.5 | 0.5 | POLYGON ((597 2568.5, 597.5 2568.5, 597.5 2569... |
| 3 | 9999.0 | 2012-07-01 | 597.75 | 2568.75 | 0.5 | 0.5 | POLYGON ((597.5 2568.5, 598 2568.5, 598 2569, ... |
| 4 | 9999.0 | 2012-07-01 | 598.25 | 2568.75 | 0.5 | 0.5 | POLYGON ((598 2568.5, 598.5 2568.5, 598.5 2569... |
| 5 | 9999.0 | 2012-07-01 | 598.75 | 2568.75 | 0.5 | 0.5 | POLYGON ((598.5 2568.5, 599 2568.5, 599 2569, ... |
Shapefile, step 2: export
# gdf.to_file('chasim.shp')
Export to raster
For one time step, user can export a regular grid as a TIFF file with function glm.to_raster
For all time steps at once, use ds.mart.to_raster(filename_tpl='chasim_hallue'), the filename template
argument must not contain any extension.
CAUTION: this is only for regular grids. For irregular/nested grids, the QGIS plugin PostMARTHE is preferable to save chasim as .tiff It will save the results in raster file with the smallest resolution available in all nested grids.
help(gm.to_raster) # function doc to write a raster file
Help on function to_raster in module gridmarthe.grid.processing.gis:
to_raster(ds, varname=None, x_dim='x', y_dim='y', time=None, epsg=27572, filename_tpl='raster')
Write a xr.DataArray to a raster file
Notes
-----
- Warning, only functionnal for regular grids
- Requires rasterio/rioxarray packages
- TODO: add support for irregular grids, using PostMARTHE QGIS plugin code.
Parameters
----------
ds : xarray.Dataset, xarray.DataArray
The dataset/dataArray to write to a raster file
x_dim : str, optional
The name of the x dimension, by default 'x'.
y_dim : str, optional
The name of the y dimension, by default 'y'.
time : str, list
time or list of time from `da.time`
epsg : int, optional
The EPSG code for the coordinate reference system, by default 27572.
filename_tpl : str, optional
The output file template for the raster file, by default 'raster'.
Final name will be '{filename_tpl}_{time}.tiff'
Returns
-------
None
The function writes the raster file and returns None.
CLI for gis transformation
A command line script is also provided to transform a marthe grid file to shapefile or geopackage.
!martshp -h
usage: martshp [-h] [--output OUTPUT] [--varname VARNAME]
[--xyfactor XYFACTOR] [--gpkg] [--mask] [--version]
[--wide_fmt]
[grid timesteps ...]
Convert a Marthe GridFile to shapefile format.
positional arguments:
grid timesteps Paths to marthe grid [and timesteps if result] files
are expected.If input is already a netcdf file, this
script allow the conversion to shapefile/gpkg.
options:
-h, --help show this help message and exit
--output OUTPUT, -o OUTPUT
Output filename. Default is input.nc
--varname VARNAME, -n VARNAME
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.
--xyfactor XYFACTOR, -x XYFACTOR
Transformation factor for coordinates. Optional,
default is 1 (no transformation).
--gpkg, -g Use GPKG format instead of shapefile
--mask, -m Only get a mask of active domain
--version, -v Show version and exit
--wide_fmt, -w Use wide format (columns) for time
gridmarthe Copyright (C) 2025 BRGM.
This program comes with ABSOLUTELY NO WARRANTY.
This is free software, see GNU General Public Lisence v3 for copying.