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I am mapping mountainous areas in QGIS 2.4 and would like to recreate the beautiful blended colour relief found, for example, in the map shown at http://maps.kartoza.com/Boosmansbos/.

While I am able to copy the RGB values of the colours from the key at the side of the map, and map them into my own elevation bands, I am unable to recreate the 'blended' effect between the elevation bands as QGIS produces a 'hard' line between elevation levels.


I'm using the basic mode I suppose which is the menu at the top, Raster - Terrain Analysis - Relief, then mapping the colour bands that way. I thought I might be able to get a 'blend' by overlapping the elevations slightly in each band, but it doesn't seem to let me do that.

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    There are two or three methods of producing elevation-coloured layers in QGIS, which one are you using? – nhopton Sep 11 '14 at 7:14
  • I'm fairly new to QGIS, I'm using the basic mode I suppose which is the menu at the top, Raster - Terrain Analysis - Relief, then mapping the colour bands that way. I thought I might be able to get a 'blend' by overlapping the elevations slightly in each band, but it doesn't seem to let me do that. – Edward Sep 11 '14 at 7:23
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    The method you're using generates hillshade and elevation colours and merges them automatically. It's very quick but it doesn't give you much control and it doesn't produce graded colours. To get the result you are looking for you will need to produce separate hillshade and elevation-coloured layers and merge them. QGIS has all the features you need to do this. I've got to rush, but if someone doesn't come back with answer I'll post some pointers later. N. – nhopton Sep 11 '14 at 8:15
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The QGIS training manual shows how to style rasters using a color ramp:

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After that, use the hillshade tool to compute a hillshade raster and set the hillshade's layer blending mode to e.g. multiply to blend both layers together. (Hillshade has to be on top in that case.)

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    I'm curious why using the blending mode is the recommended method rather than adjusting the top layer's opacity? Wouldn't the latter provide more flexibility in display? – WhiteboxDev Sep 11 '14 at 21:55
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    @WhiteboxDev the blending mode (multiply) allows the gradient DEM to overlay the hillshade without losing much saturation, the original colours won't have that washed out look. That's something cartographers often do in external graphics editing programs making map making a tedious process. – SaultDon Sep 11 '14 at 21:59
  • @SaultDon, Hmmm, very interesting. In previous editions of my software I have included a tool to create an RGB colour composite using this approach but then removed it as I supported transparency, which I found to be more flexible. Makes me think I should bring that tool back! – WhiteboxDev Sep 11 '14 at 22:04
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    @WhiteDev I think in the palette (on the left) you see five distinct classes but it can be controlled by the user when changing from "Continuous" to "Equal Interval" and in this case defaults to 5, but is still uses a "linear" option to blend them together. I think QGIS can be improved to show a gradient in the legend on the print composer because it still shows the distinct classes when using linear colour blending. – SaultDon Sep 11 '14 at 22:12
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    @WhiteboxDev it makes it also interesting because you can change the numbers in the "value" column to determine where those colours blend into each other based on elevation. – SaultDon Sep 11 '14 at 22:13

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