demqgistopography
I am using Mapzen global terrain to create a topographic map.
How can I get a very simplified result like on the map of Greece?
Should I use contours lines ? And how to smooth them ? (wich algorithm to use ?).
What I have:
What I want :
What I tried :
Scale reduction in symbology (but i am still in raster mode)
There are a couple of ways to make your contours smoother.
Looking at the contours, I suspect it's because the IDW raster is low resolution. Did you use the default size (300x300) when creating this?
Resize your IDW raster
Probably the easiest way :-
You should now have smoother contours.
Generalizer plug-in
Another thing to check is the 'Generalizer' plugin and apply it to your existing contours. This has several smoothing options, but it is a bit more involved (you'll need to experiment to get good settings)
You might want to check out this question to see how this works.
I think the problem is related to how you change the projection of your data. If the DEM data was originally in geographic projection (WGS84), and not projected to UTM zone 10S, then you need to reproject the original DEM image (the WGS84) again in a proper way. When you reproject (Warp) the DEM from geographic to UTM projection, it is better that you choose "Cubic" as a Resampling Method - sometimes the method called "Cubic Convolution" - especially for continuous data like DEM.
I think using proper resampling method when reprojecting the DEM will solve the problem.
Best Answer
Solution 1: Discrete layer Styling
Simply create the effect using layer style: set it to singleband pseudocolor, choose a white to black color ramp and manually classify depending on the elevation values you want to group together:
See how to do it; additionally, I set a transparency value of 100% for values -9999 to 0 to render the sea transparent to make the OpenStreetMap background visible there:
Solution 2: Reclassify
Run Reclassify by Table and define the elevation values for which you want to groupt together to a single elevation class, e.g. like in the screenshot.
To "smooth", use Majority filter, see this answer for details.
Result after step 1, based on Mapzen Global Terrain and the reclassification table you can see:
Solution 3: Contour polygons
Alternatively, you can create contour polygons:
See this answer how to create contour polygons.
As an option, use
smooth()with Geoemtry Generator to get smoother forms.Contour polygons after step 1 with interval 500 meters, deleted those below sea level, color with data driven override > assistant set to field
ELEV_MAX(automatically created by the contour polygon algorithm) and values from 0 to 3500 with a withe to black color ramp: