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I have a full set of the old half-Inch Scale John Bartholomew maps produced up to the early 1970s (1972 - 1974) of Great Britain, and I'd like to produce new mapping in the same style, but with modern Sans Serif settlement labels and fully up-to-date roads using Ordnance Survey free Open Esri Shape Data.

In particular, I want to make the map with the Contour Lines and Stepped Hypsometric Tints that John Bartholomew used - Bartholomew used non-uniform contour interval that varied with the height above sea level.

Is it possible to make Custom Contours with variable intervals in feet from DEM or other Elevation Data, or is QGIS restricted to one Contour Interval in metric units only?

The reason for this is a personal subjective one - I feel that elevation in feet gives a better 'feel' of the relatively modest range of elevation in the British Isles than contours in metres do.

If QGIS can't do it, is there another mapping application that can?

  • GMT can do custom contours by defining levels in a file: gmt.soest.hawaii.edu/doc/latest/grdcontour.html – JimT Aug 4 '18 at 21:43
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    This is the oumost basic math, do your contours at 0.305 interval. – FelixIP Aug 5 '18 at 4:10
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    QGIS can do all of the things you mention, but if you're starting from scratch you have quite a lot of learning to do. If I were you I'd suggest posting each of your queries in a separate post, say one for extracting contours in feet from DEMs having elevation values in metres, one for colouring by elevation and so on. But first read the manual, do some Googling and have a look at QGIS on YouTube. Good luck. – nhopton Aug 5 '18 at 8:34
  • An afterthought. Once you've done some reading probably the first question to ask is what appropriate, free datasets are available for your project? – nhopton Aug 5 '18 at 9:34
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Is it possible to make Custom Contours with variable intervals in feet from DEM or other Elevation Data, or is QGIS restricted to one Contour Interval in metric units only?

Yes, but not the usual QGIS contouring. Normal contouring assumes regular contours. However, Grass r.contour (available in QGIS via processing) does allow you to specify a list of specific contour levels which don't need to be regular e.g. 10,20,50,100,200...

For contouring purposes, QGIS doesn't know (or care) what vertical units are.

As @FelixIP points out, you can either set your contour levels by dividing the meters value (OS elevations are in meters) by 0.305 (or multiplying by 3.279). You can do this manually, or you can use Raster Calculator to divide all the elevations by 0.305 - your raster elevations are now in feet and you can apply contours using values in feet.

Note that if you do this, this may affect things like hillshading and 3d visualisation (you're effectively stretching the terrain vertically by a factor of 3), although I don't recall those maps being hillshaded. In either case, you can simply change the vertical exaggeration setting to 0.305 to convert back to meters for hillshading.

I assume here you'd be using the OS Open Terrain 50 product for terrain). Here, the contours are 10 feet apart. I used the wiki-schawrzwald-d050 colour ramp as it's the closest built-in one to how I remember their style.

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