Hi all.
I found a strange render artifact on a topo map, and it can be seen anywhere along latitude 43.068, in both hemispheres.
The most noticeable is on Tracestrack topo map, for example, here: OpenStreetMap
It can also be seen on CycleOSM map as isolines breaks, but it isn’t really conspicuous.
Screenshot of these artifacts:
Tracestrack topo on the left, CycloOSM on the right.
Does that mean that something is wrong with the topography data?
And where this bug might come from? 43.068 doesn’t even look like a fraction of some good angles
It seems to be based off of the raster tile boundaries. With a quick check, it seems that the contours are broken at z8 tile boundaries, at least on the N-S axis. See OpenStreetMap, which is the next tile edge south.
This is not tile boundaries, but DEM tiles boundaries.
When calculating contour lines from a raster DEM, you will see artefacts at the edge of the DEM tiles if the calculation doesn’t take the neighbour tile into account to find the ‘same altitude line’.
