Support custom mapping from UCD to WSCAxes properties for custom coordinate frames

What is the problem this feature will solve?

The overall aim is to have nice plot with proper ax.coords setting e.g. coord_wrap, format_unit, coord_type for custom Coordinate frames.

Currently half of the is supported, fitswcs.py supports custom ctype to UCD mappings via CTYPE_TO_UCD1_CUSTOM but then on the other side wscapi.py has a hard coded list in transform_coord_meta_from_wcs therefore WCSAxes doesn't recognise the custom UCD.

So currently this can be done

MYFRAME_CTYPE_TO_UCD1 = {
    "SXLT": "custom:pos.myframe.lat",
    "SXLN": "custom:pos.myframe.lon",
    "SXRZ": "custom:pos.myframe.z"
}
astropy.wcs.wcsapi.fitswcs.CTYPE_TO_UCD1_CUSTOM.update(MYFRAME_CTYPE_TO_UCD1)

but there is no way to include settings for custom:pos.myframe.X in this section of code

astropy/astropy/visualization/wcsaxes/wcsapi.py

Lines 54 to 71 in cf99b9e

    
           for idx in range(wcs.world_n_dim): 
        
               axis_type = wcs.world_axis_physical_types[idx] 
        
               axis_unit = u.Unit(wcs.world_axis_units[idx]) 
        
               coord_wrap = None 
        
               format_unit = axis_unit 
        
               coord_type = "scalar" 
        
               if axis_type is not None: 
        
                   axis_type_split = axis_type.split(".") 
        
                   if len(axis_type_split): 
        
                       axis_type_split[0] = axis_type_split[0].replace("custom:", "") 
        
                   if "pos.helioprojective.lon" in axis_type: 
        
                       coord_wrap = 180.0 * u.deg 
        
                       format_unit = u.arcsec 
        
                       coord_type = "longitude" 
        
                   elif "pos.helioprojective.lat" in axis_type:

where Id like to add something like

            if "custom:pos.MYFRAME.lon" in axis_type:
                coord_wrap = 180.0 * u.deg
                format_unit = u.arcsec
                coord_type = "longitude"
            elif "custom:pos.MYFARME.lat" in axis_type:
                format_unit = u.arcsec
                coord_type = "latitude"

Describe the desired outcome

Be able to register or other wise include custom plot setting for custom UCDs in a similar manner to how custom CTYPE to UCD mapping can be included.

Additional context

No response

In a slack discussion the concept of extending the context manager approach as used here

astropy/astropy/wcs/wcsapi/fitswcs.py

Line 165 in cf99b9e

class custom_ctype_to_ucd_mapping:

and here

astropy/astropy/wcs/utils.py

Line 273 in cf99b9e

class custom_wcs_to_frame_mappings:

was mentioned. I wonder if in addition to this approach underlying lists and dictionaries could be exposed and documented that way other packages could add / remove mappings without relying on astropy. For example some sunpy specific mapping can be found here

astropy/astropy/wcs/wcsapi/fitswcs.py

Lines 117 to 126 in cf99b9e

    
           "HPLT": "custom:pos.helioprojective.lat", 
        
           "HPLN": "custom:pos.helioprojective.lon", 
        
           "HPRZ": "custom:pos.helioprojective.z", 
        
           "HGLN": "custom:pos.heliographic.stonyhurst.lon", 
        
           "HGLT": "custom:pos.heliographic.stonyhurst.lat", 
        
           "CRLN": "custom:pos.heliographic.carrington.lon", 
        
           "CRLT": "custom:pos.heliographic.carrington.lat", 
        
           "SOLX": "custom:pos.heliocentric.x", 
        
           "SOLY": "custom:pos.heliocentric.y", 
        
           "SOLZ": "custom:pos.heliocentric.z",

and sunpy already directly adds custom frames mappings to the lists

astropy/astropy/wcs/utils.py

Lines 269 to 270 in cf99b9e

    
           WCS_FRAME_MAPPINGS = [[_wcs_to_celestial_frame_builtin]] 
        
           FRAME_WCS_MAPPINGS = [[_celestial_frame_to_wcs_builtin]]

here

https://github.com/sunpy/sunpy/blob/5b27fef34b9f36256da4037ba27b0bece61e755a/sunpy/coordinates/wcs_utils.py#L206-L207

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Support custom mapping from UCD to WSCAxes properties for custom coordinate frames #16339

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	for idx in range(wcs.world_n_dim):
	axis_type = wcs.world_axis_physical_types[idx]
	axis_unit = u.Unit(wcs.world_axis_units[idx])
	coord_wrap = None
	format_unit = axis_unit

	coord_type = "scalar"

	if axis_type is not None:
	axis_type_split = axis_type.split(".")
	if len(axis_type_split):
	axis_type_split[0] = axis_type_split[0].replace("custom:", "")

	if "pos.helioprojective.lon" in axis_type:
	coord_wrap = 180.0 * u.deg
	format_unit = u.arcsec
	coord_type = "longitude"
	elif "pos.helioprojective.lat" in axis_type:

	"HPLT": "custom:pos.helioprojective.lat",
	"HPLN": "custom:pos.helioprojective.lon",
	"HPRZ": "custom:pos.helioprojective.z",
	"HGLN": "custom:pos.heliographic.stonyhurst.lon",
	"HGLT": "custom:pos.heliographic.stonyhurst.lat",
	"CRLN": "custom:pos.heliographic.carrington.lon",
	"CRLT": "custom:pos.heliographic.carrington.lat",
	"SOLX": "custom:pos.heliocentric.x",
	"SOLY": "custom:pos.heliocentric.y",
	"SOLZ": "custom:pos.heliocentric.z",

	WCS_FRAME_MAPPINGS = [[_wcs_to_celestial_frame_builtin]]
	FRAME_WCS_MAPPINGS = [[_celestial_frame_to_wcs_builtin]]

Support custom mapping from UCD to WSCAxes properties for custom coordinate frames #16339

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What is the problem this feature will solve?

Describe the desired outcome

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samaloney commented on Apr 25, 2024

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