Module normalise 

Normalisation: find a cheaper, equivalent mapping for what was stored.

Readers record the stored form (the “costume” in regular-in-what). Normalisation tests whether it is really a lower rung, within a stated tolerance, and if so adds the cheaper mapping alongside the stored one and marks it primary. Every test returns a Report, accepted or not, so it is always visible why a grid was labelled what it was.

Three tests are provided:

• regular_axis: a 1D coordinate vector is evenly spaced (R2 to R1; GDAL’s IsRegularlySpaced and GuessGeoTransform);
• regular_axis_through: evenly spaced after a 1D change of frame (AVISO’s latitude vector is regular in Mercator y);
• regular_grid_through: 2D coordinate arrays are an affine grid after a change of frame (cryptic curvilinear to R1, the NSIDC case).

The frame change is a plain function supplied by the caller, so this crate needs no CRS backend.

Structs

Report

The outcome of one normalisation test.

Enums

Tolerance

How far stored coordinates may sit from the fitted mapping.

Functions

affine_from_axes

An affine transform from the primary mappings of a row dim and a col dim, when both are R1 (Regular1) in the same frame.

normalise_domain

The conservative default (design doc 02, gate 2 default 3): every 1D rectilinear mapping that is evenly spaced within Float32 tolerance gains a regular mapping, marked primary. Stored mappings are kept.

normalise_domain_with

As normalise_domain, with a chosen tolerance.

regular_axis

Test whether a 1D coordinate vector is evenly spaced.

regular_axis_through

Test whether a 1D coordinate vector is evenly spaced after applying f to every value (for example latitude to Mercator y). through names the frame f maps into. On success the returned positions are in that frame.

regular_grid_through

Test whether 2D coordinate arrays (centres, shaped [nrow, ncol]) form an affine grid after mapping each (x, y) pair through f. through names the frame f maps into. None from f fails the test.