May not be a OSM issue as the tools (gdal_contour and mapnik) are not specifically OSM, but I got started on it by following https://wiki.openstreetmap.org/wiki/Contour so I’ll ask here. . .
I’ve been able to setup a style to render major and minor contour lines with the major lines having the elevation value displayed however the elevation is being displayed as a non-integer value (e.g. 8000.0 rather than 8000). These are in feet having converted the DEM data from meters using gdal_translate before generating the contours with gdal_contour but I can’t imagine that this should have any effect on my problem.
None of the examples I can find show a non-integer value on their results, Neither gdal_contour nor mapnik documentation seem to have controls for this formatting. Not sure if gdal_contour is saving the elevation as a string already formatted or if mapnik is converting a number into a string even so I don’t even know where to dig deeper.
Any suggestions on how to affect the formatting of the elevation value beyond the font, font size, etc. that are in the mapnik styling XML?