Misoriented altitude labels on contour lines

[maze88]

How to reproduce the issue?

On OSM, with any layer (including tracetrack's) that shows contour lines active, some of the lines' altitude labels are misoriented. This issue can cause confusion, since it deviates from the convention of topographical map notation (source).

Current behavior

The current logic appears to be "display the contours' labels perpendicular to their line, in the orientation that is most readable on the viewer's screen".

Expected bahavior

All the number labels on contours should be aligned with the top of the number uphill.

Screenshot(s) or anything else?

In the following screenshot (of an obvious mountain) I have marked in green and in red contours that are and are not (respecively) oriented correctly - relative to the mountain peak.

Link to map: https://www.openstreetmap.org/#map=18/29.78000/34.96927&layers=P

[quinncnl]

Hi @maze88 , thanks for the report. So you'd like to render the red labels upside down? It makes good sense but technically it's difficult. We'll need to somehow let mapnik know which side is uphill. I'll check if that's possible.

[maze88]

Hi @maze88 , thanks for the report. So you'd like to render the red labels upside down? It makes good sense but technically it's difficult. We'll need to somehow let mapnik know which side is uphill. I'll check if that's possible.

Yes, perhaps best I report it in their repository then...

[yvecai]

For what it's worth, I received the same comment about contour lines at Opensnowmap this winter.
The only rendering I found following the so-called 'convention' was https://opentopomap.org/#map=16/46.79407/6.48537
For known references, French IGN maps does one way, Swisstopo the other way. Looking close to the border, you can see the orientation differences:
https://www.geoportail.gouv.fr/carte?c=6.342404224843148,46.708998996879075&z=15&l0=GEOGRAPHICALGRIDSYSTEMS.MAPS.SCAN25TOUR.CV::GEOPORTAIL:OGC:WMTS(1)&permalink=yes

Honestly, I don't see anything weird one way or another, so that's a good idea if it can improve relief readability.