Convert Canadian ice service (CIS) ESRI shapefiles to ascii format (dex).

CIS daily ice analysis charts (dailys) and regional analysis charts (weeklys) are collected every day on mixing and processed to provide information such as,

• Ice thickness maps.
• First occurence maps.
• Total gulf, Newfoundland shelf and Scotian Shelf ice volumes.
• Comparisons to climatology.

These analyses are performed by a combination of Perl/awk routines and are facilitated by first transforming the shapefiles to gridded ascii plain text in a format called dex, containing geographical coordinates and egg code data. Time information is carried by the file name (YYYYMMDD) and the columns in the file are ordered as follows,

1. Longitude (west)
2. Latitude
3. Total ice concentration
4. Partial ice concentration (thickest ice)
5. Stage of developpment (thickest ice)
6. Form of ice (thickest ice)
7. Partial ice concentration (second thickest ice)
8. Stage of developpment (second thickest ice)
9. Form of ice (second thickest ice)
10. Partial ice concentration (third thickest ice)
11. Stage of developpment (third thickest ice)
12. Form of ice (third thickest ice)

This module performs the conversion and is meant to be called from command line. Command line interface description can be shown by entering,

$ shp2dex -h

Create a virtual environment containing this package's dependencies. In conda, either

conda create -n shp2dex Python=3.12 pandas=2.2.2 cartopy=0.23.0 termcolor=2.4.0 xarray=2024.7.0

should install all the appropriate dependencies. Alternatively, you can use the provided yml file to build the environment, i.e.,

conda env create -f requirement.yml

the output of pip freeze > requirements.txt is also included for pip users. Once the environment is set up, navigate to the site-packages folder and clone this repository.

cd /path/to/anaconda/envs/shp2dex/lib/python3.12/site-packages
git clone https://github.com/jeanlucshaw/shp2dex.git shp2dex

For this utility to be available at the command line, add a file called shp2dex on your shell path, for example at /usr/local/bin/ containing the following lines,

#!/path/to/bash
/path/to/python /path/to/shp2dex/shp2dex.py "$@"

To test the installation, run shp2dex -h from the command line or run the included examples of command-line and scripted use cases.

More background information can be found at the following links:

• About the Egg code and CIS data products

• About the SIGRID-3 shapefile format used by the CIS

• CIS sea ice glossary

Have a look at

• example_python.py
• example_julien.py

which demonstrate use of this module as part of a Python script, and at

• example_shell.sh

which demonstrates how to use the module via its command line interface.

Although advantageous for software designed to ingest it, the .dex format can be cumbersome to integrate to new software because it mixes string characters and numbers in some data columns, and has different numbers of columns accros its rows. To facilitate the use of existing .dex file data bases, the dex2nc module included in this package reads the .dex format into xarray dataset objects. Conversion to netCDF, a common format for the storage of raster data can then be performed via user scripts:

from shp2dex.dex2nc import dex2ds

ds = dex2ds('my_file_YYYYMMDD.dex')
ds.to_netcdf('my_file_YYYYMMDD.nc')

or using the module as a command line application

$ python /path/to/dex2nc.py /path/to/my_file_YYYYMMDD.dex
$ python /path/to/dex2nc.py /path/to/*.dex