Definition of "spherical_cs" (missing)

NOTE: Markdown does not support highlighting in color, so bold/italic has been used to highlight the material being discussed. This issue is extracted from the document submitted by Roger Lott at https://github.com/opengeospatial/CRS-JSON-Encoding/blob/main/ProjJson%20v0-7%20RL%202024-06-16.docx for discussion at the CRS SWG meeting OGC held during the Montreal June 2024 TC meeting.

"spherical_cs": { }

"$comment": "[RL] Definition to be completed. The definition should constrain a spherical CS to have 2 or 3 axes.
When a spherical CS is used within a geodetic CRS, 19111/Topic2 constrains axis names (see Topic 2 Table 27). WKT2 requires that axis abbreviations be from the Latin character set and recommends that axis abbreviations φ and θ are be replaced by U and V."

Start with the “spherical_cs” fragment in the issue and the linked ProjJson v0-7 document. Check 19111/Topic2 Table 27 and the WKT2 axis-abbreviation guidance referenced there; the definition is done when it constrains spherical coordinate systems to two or three axes and documents the applicable naming rules.