[SIS-552] Better identification of latitude/longitude axes in netCDF

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.0, 1.1, 1.2
• Fix Version/s: 1.3
• Component/s: Storage
• Assignee: Martin Desruisseaux
• Reporter: Martin Desruisseaux
• Created: 08/Jul/22 14:16
• Updated: 07/Dec/22 18:31
• Resolved: 08/Jul/22 15:33

Description

The Coordinate Reference System inferred by the parsing of a netCDF file is sometime of type EngineeringCRS when it should be GeographicCRS. This is caused by AxisType using the following criteria in that order:

• Value of _CoordinateAxisType attribute, which may be "GeoX" or "GeoY" among others.
• Value of axis attribute, which may be "X" or "Y" among others.
• Value of standard_name attribute, which may be "longitude" or "latitude" among others.
• Value of description, title or long_name attribute.
• Unit of measurement, which may be "degrees_east" or "degrees_north" among others.

The problem occurs when we find an axis attribute with value "X" or "Y", which is used in CF convention not only for latitude/longitude, but also for other kind of horizontal axes. Apache SIS conservatively assumes an engineering CRS as the closest match for CRS of unknown type.

According CF conventions, the "degrees_east" and "degrees_north" units of measurement should be tested first. We should modify AxisType for using that order.