Relief maps

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Relief map example tile2.jpg
Relief map example tile.jpg
Example tiles (source)

Relief maps are maps with each pixel colour-coded according to the ground height and/or slope at that location. Generally height is shown in a combination of three concepts: contours, colouring and shading.

There is not much height data available from OSM, due to the poor vertical accuracy of GPS units compared to both their horizontal accuracy and the better height data available from other sources. Accurate spot heights, for example mountain summits, are often available from other sources, but wide-scale height data sufficient for making profiles of mountains are simply infeasible to gather by volunteers wandering around! For such data, existing OSM projects normally rely on SRTM data, a near-globally available height dataset from NASA that has been released into the public domain.

Since there are many algorithms to interpret the height data sets (DEMs), and different purposes have different algorithms, data from such sets should NOT be uploaded to OSM (e.g. no ele=* tagging of nodes from SRTM data, or adding contours as ways)!

Colour coding and shading

  • colorized by altitude (as seen in example on top right)
  • shaded relief (levels of gray), just to indicate relative slopes, mountain ridges, not absolute height.

Relief-height.png+Relief-shade.png=Relief-shade-height.png

Elevation contour lines

See Srtm2Osm; e.g.:

Etna Contours.jpg

See also

OSM maps showing relief

Existing software

Interesting articles and examples

See also