There is another notation for feet, ' (ASCII apostrophe), that is 40 times more common on length-related keys in general (including common keys such as height=*). The “Units” page on the wiki encourages the ##'##" notation and strongly discourages ft or in.
On the other hand, the ele=* documentation currently discourages unit specifications altogether. Despite this longstanding guideline, several major data consumers support both ft and ' for specifying elevations in feet. This proposal would codify that option for mappers. It doesn’t prefer one notation over the other, but perhaps you might consider adding support for ' for completeness.
checkele()currently recognizesftas the notation for feet withinele=*, converting it to meters:https://github.com/der-stefan/OpenTopoMap/blob/e4467cfc2064afc379b0f8e8360db1740099cca3/mapnik/tools/isolation.c#L65 https://github.com/der-stefan/OpenTopoMap/blob/e4467cfc2064afc379b0f8e8360db1740099cca3/mapnik/tools/isolation.c#L78
There is another notation for feet,
'(ASCII apostrophe), that is 40 times more common on length-related keys in general (including common keys such asheight=*). The “Units” page on the wiki encourages the##'##"notation and strongly discouragesftorin.On the other hand, the
ele=*documentation currently discourages unit specifications altogether. Despite this longstanding guideline, several major data consumers support bothftand'for specifying elevations in feet. This proposal would codify that option for mappers. It doesn’t prefer one notation over the other, but perhaps you might consider adding support for'for completeness.