iris: Error loading NSDIC-0116-nh data. CRS AXIS UNKNOWN (polar-grid)

🐛 Bug Report

I am trying to load the NSIDC-0116-nh raw data into a cube. Iris fails with the following error: This is a CRS error from pyproj (v3.5.0).

CRSError: Invalid projection: PROJCS["NSIDC EASE-Grid North",GEOGCS["Unspecified datum based upon the International 1924 Authalic Sphere",DATUM["Not_specified_based_on_International_1924_Authalic_Sphere",SPHEROID["International 1924 Authalic Sphere",6371228,0,AUTHORITY["EPSG","7057"]],AUTHORITY["EPSG","6053"]],PRIMEM["Greenwich",0,AUTHORITY["EPSG","8901"]],UNIT["degree",0.01745329251994328,AUTHORITY["EPSG","9122"]],AUTHORITY["EPSG","4053"]],UNIT["metre",1,AUTHORITY["EPSG","9001"]],PROJECTION["Lambert_Azimuthal_Equal_Area"],PARAMETER["latitude_of_center",90],PARAMETER["longitude_of_center",0],PARAMETER["false_easting",0],PARAMETER["false_northing",0],AUTHORITY["EPSG","3408"],AXIS["X",UNKNOWN],AXIS["Y",UNKNOWN]]: (Internal Proj Error: proj_create: unhandled axis direction: UNKNOWN)

Full Traceback: traceback.txt

How To Reproduce

Steps to reproduce the behaviour:

Download data from https://nsidc.org/data/nsidc-0116/versions/4

import iris 
cubes = iris.load("icemotion_daily_nh_25km_19790101_19791231_v4.1.nc")

Expected behaviour

Should load data.

Screenshots

Environment

Iris Version: 3.6.0

Additional context

This is used by the NSDIC cmoriser in ESMValTool

About this issue

Original URL
State: closed
Created a year ago
Comments: 24 (9 by maintainers)

Commits related to this issue

Add note for the NSDIC cmoriser (requires PROJ9.3) see https://github.com/SciTools/iris/issues/5343 — committed to ESMValGroup/ESMValTool by rbeucher 7 months ago
Add note for the NSDIC cmoriser (requires PROJ9.3) see https://github.com/SciTools/iris/issues/5343 — committed to ESMValGroup/ESMValTool by rbeucher 7 months ago

Most upvoted comments

pyproj4/pyproj#1328

trexfeathers on Jul 27, 2023

Thanks for sending the file over. This enabled us to step through and experiment; the problem is because Proj does not accept leading spaces in WKT strings, so the crs_wkt attribute on the crs variable:

 PROJCS["NSIDC EASE-Grid South",GEOGCS["Unspecified datum based upon the International 1924 Authalic Sphere",DATUM["Not_specified_based_on_International_1924_Authalic_Sphere",SPHEROID["International 1924 Authalic Sphere",6371228,0,AUTHORITY["EPSG","7057"]],AUTHORITY["EPSG","6053"]],PRIMEM["Greenwich",0,AUTHORITY["EPSG","8901"]],UNIT["degree",0.01745329251994328,AUTHORITY["EPSG","9122"]],AUTHORITY["EPSG","4053"]],UNIT["metre",1,AUTHORITY["EPSG","9001"]],PROJECTION["Lambert_Azimuthal_Equal_Area"],PARAMETER["latitude_of_center",-90],PARAMETER["longitude_of_center",0],PARAMETER["false_easting",0],PARAMETER["false_northing",0],AUTHORITY["EPSG","3409"],AXIS["X",UNKNOWN],AXIS["Y",UNKNOWN]]

… is invalid. If the leading space is removed, the file loads fine.

Iris has been handling WKT for over a year (#4704) but this is the first time the problem has been reported, which suggests that either:

Most crs_wkt attributes are correctly formatted for Proj to handle.
Users don’t often use Iris to load files with crs_wkt attributes.

I’d like to draw on ESMValTool’s rich experience with file formats here: would you expect this problem to crop up more often in future, or is there a specific problem with NSIDC-0116-nh files?

trexfeathers on Jul 27, 2023

@rbeucher just to let you know we have some scheduled time to investigate this later in the month.

trexfeathers on Jul 5, 2023

I could also reproduce this with iris 3.4.1 and 3.6.0, used in recent ESMValTool installations. The dataset could be loaded successfully with iris 3.2.1 that we were using for ESMValTool v2.7

remi-kazeroni on Jun 14, 2023