[ndcube migration] Add a `.wcs` setter which updates `.meta` by Cadair · Pull Request #8819 · sunpy/sunpy

Cadair · 2026-09-15T20:50:12Z

This functionality is needed to support NDCube methods which modify the WCS (with APE 14 wrappers), i.e. rebin, __getitem__, crop etc.

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samaloney · 2026-10-16T16:13:59Z

+    # oldestdeps - asdf-astropy 0.7 uses astropy's deprecated TestRunner on import. This must
+    # come before any filter that imports sunpy/astropy (e.g. SunpyConnectionWarning) as
+    # resolving those categories triggers the import and the "error" filter is already active.
+    ignore:The TestRunner(Base)? class will be deprecated:PendingDeprecationWarning


the alternative is bump asdf-astropy

Cadair · 2026-10-21T16:28:37Z

+        # relax=True so non-standard keywords (e.g. SIP) are kept rather than warned about
+        new_header = unwrapped.to_header(relax=True)
+        for n in range(1, unwrapped.naxis + 1):
+            new_header[f"NAXIS{n}"] = unwrapped._naxis[n - 1]
+            # The new WCS may not have preserved units (e.g. it is in degrees), so
+            # convert it into the units the metadata already uses.
+            meta_unit = self.meta.get(f"cunit{n}")
+            # Sources declare how their CUNIT should be read by overriding
+            # `spatial_units`, e.g. EIT omits it and LASCO uses a non-FITS 'ARCSEC',
+            # so convert to that rather than parsing the raw keyword.
+            target_unit = self.spatial_units[n - 1] if n <= len(self.spatial_units) else None
+            if target_unit is None and meta_unit is not None:
+                target_unit = u.Unit(meta_unit)
+            if meta_unit is None and target_unit is not None:
+                meta_unit = target_unit.to_string()
+            header_unit = new_header.get(f"CUNIT{n}")
+            if target_unit is None or header_unit is None:
+                continue
+            factor = u.Unit(header_unit).to(target_unit)
+            if factor != 1:
+                keys = [f"CDELT{n}", f"CRVAL{n}"]
+                keys += [f"CD{n}_{m}" for m in range(1, unwrapped.naxis + 1)]
+                for key in keys:
+                    if key in new_header:
+                        new_header[key] *= factor
+                new_header[f"CUNIT{n}"] = meta_unit


@samaloney Am I right in thinking that all this section can be removed if we bump an astropy bugfix release or two?

some of it still need a special case for EIT I think

…ict (thanks whoever wrote #8844)

Replace unit conversion with a guard that rejects differing spatial units before modifying metadata. Retain source handling for updated GONG scales and EIT radius calculations.

Cadair · 2026-11-11T17:32:34Z

@@ -0,0 +1,3 @@
+`~sunpy.map.GenericMap.wcs` now keeps the units of the map's metadata (usually arcseconds) instead of converting to degrees.
+Raw world values, such as ``map.wcs.wcs.cdelt`` or values passed to ``ax.get_transform('world')``, are now in those units.


"values pass to ax.get_transform("world")" is a weird way to write this, we should say "when plotting values with ax.get_transform" or something.

Cadair added this pull request to stack #8810 September 15, 2026 20:50

Cadair force-pushed the map-refactor/wcs-setter branch from 0060326 to ef2727b Compare September 15, 2026 20:54

Cadair removed this pull request from stack #8810 September 15, 2026 20:57

Cadair changed the base branch from map-refactor/ndcube-constructor to map-refactor/ndcube-base September 15, 2026 20:57

Cadair force-pushed the map-refactor/wcs-setter branch from ef2727b to c1aa6ad Compare September 15, 2026 20:57

Cadair added this pull request to stack #8820 September 15, 2026 20:57

Cadair changed the title ~~Add wcs setter and test with SlicedLowLevelWCS~~ Add a .wcs setter and test with SlicedLowLevelWCS Sep 15, 2026

Cadair changed the title ~~Add a .wcs setter and test with SlicedLowLevelWCS~~ Add a .wcs setter which updates .meta Sep 15, 2026

Cadair changed the title ~~Add a .wcs setter which updates .meta~~ [ndcube-migration] Add a .wcs setter which updates .meta Sep 15, 2026

Cadair added map Affects the map submodule No Backport A PR that isn't to be backported to any release branch. (To be used as a flag to other maintainers) labels Sep 15, 2026

Cadair mentioned this pull request Sep 16, 2026

Map ndcube map migration rebase #8798

Open

alasdairwilson force-pushed the map-refactor/wcs-setter branch from 4a21db6 to 4564caa Compare September 16, 2026 13:00

alasdairwilson changed the title ~~[ndcube-migration] Add a .wcs setter which updates .meta~~ [ndcube migration] Add a .wcs setter which updates .meta Sep 16, 2026

samaloney force-pushed the map-refactor/wcs-setter branch from 4564caa to 432ee94 Compare October 1, 2026 09:18

Cadair force-pushed the map-refactor/wcs-setter branch from 432ee94 to 617b012 Compare October 14, 2026 18:15

alasdairwilson marked this pull request as ready for review October 14, 2026 18:26

samaloney force-pushed the map-refactor/wcs-setter branch from 617b012 to c79f74a Compare October 15, 2026 15:03

Cadair added the pre-commit.ci autofix Automatically fix pre-commit issues on this PR. label Oct 15, 2026

pre-commit-ci Bot removed the pre-commit.ci autofix Automatically fix pre-commit issues on this PR. label Oct 15, 2026

Cadair force-pushed the map-refactor/wcs-setter branch from 55476fc to f4a336c Compare October 15, 2026 15:36

samaloney force-pushed the map-refactor/wcs-setter branch from f4a336c to 26ab995 Compare October 16, 2026 09:51

samaloney force-pushed the map-refactor/wcs-setter branch 2 times, most recently from 157e570 to b8864d5 Compare October 16, 2026 15:00

samaloney reviewed Oct 16, 2026

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alasdairwilson mentioned this pull request Oct 20, 2026

[ndcube migration] Switch map.superpixel to use NDCube.rebin #8850

Open

alasdairwilson force-pushed the map-refactor/wcs-setter branch from 23018de to de58112 Compare October 20, 2026 21:47

Cadair force-pushed the map-refactor/wcs-setter branch from de58112 to d1f0cfc Compare October 21, 2026 16:21

Cadair commented Oct 21, 2026

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Cadair force-pushed the map-refactor/wcs-setter branch from d1f0cfc to 89db5f5 Compare October 21, 2026 16:47

alasdairwilson force-pushed the map-refactor/wcs-setter branch 2 times, most recently from 19141be to d55c4fe Compare October 27, 2026 19:07

alasdairwilson and others added 15 commits November 3, 2026 16:10

missed one

40cdc3a

Add wcs setter and test with SlicedLowLevelWCS

2ae823f

fix WCS setter to handle wcs=None and set NAXIS

6138c6d

Keep map WCS in metadata units with preserve_units

7b40a07

Draw same-frame quadrangles in the axes' world units

420a067

Use relax=True when comparing WCS headers in setter

1fb7206

Deal with seqfault with preserve_units

d6b60fa

Update pytest warning filters

688d86c

figure tests

2fc8806

changelogs

89a31dd

fix wcs cache screwing up wcs replacements by not popping the right d…

94c16cd

…ict (thanks whoever wrote #8844)

changelog fix

30b581c

change examples to be independent of wcs units

005dcb0

bump astropy to 7.2.3/8.0.2

86a6812

remove more pre astropy 7.2.3 / 8.0.2 code

f164a0a

Cadair force-pushed the map-refactor/wcs-setter branch from ce4e7ba to f164a0a Compare November 3, 2026 16:10

hayesla reviewed Nov 4, 2026

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Comment thread sunpy/map/mapbase.py Resolved

hayesla reviewed Nov 4, 2026

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Comment thread sunpy/map/mapbase.py Resolved

alasdairwilson mentioned this pull request Nov 5, 2026

Fix plotting of quantities in WCSAxes astropy/astropy#20779

Open

1 of 2 tasks

alasdairwilson and others added 3 commits November 5, 2026 14:25

address naxis and pcij not being set in some circumstances

0016837

Simplify WCS setter and preserve map units

605876e

Replace unit conversion with a guard that rejects differing spatial units before modifying metadata. Retain source handling for updated GONG scales and EIT radius calculations.

dont mutate the shared EIT fixture in test_rsun_uses_spatial_units

c254311

Cadair commented Nov 11, 2026

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[ndcube migration] Add a `.wcs` setter which updates `.meta` - #8819

[ndcube migration] Add a `.wcs` setter which updates `.meta`#8819
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		@@ -0,0 +1,3 @@
		`~sunpy.map.GenericMap.wcs` now keeps the units of the map's metadata (usually arcseconds) instead of converting to degrees.
		Raw world values, such as ``map.wcs.wcs.cdelt`` or values passed to ``ax.get_transform('world')``, are now in those units.

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Cadair commented Sep 15, 2026 •

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