Flatness

Being a regular hiker, I often wonder about the flatness of the places I visit. A few months ago, I came across an article on disruptivegeo.com detailing a complex methodology of flatness measuring in the US, based on the distance of the horizon.

Not being in the mood for fancy analyses, I took a rather easier approach: simply compute the standard deviation of a DEM inside predefined regions. I used ETOPO1 as a digital elevation model and a shapefile of European NUTS from Eurostat.

Here are the results:

nuts3
Elevation standard deviation of European NUTS3 regions.

According to this measure, the flattest regions in Europe are Kingston upon Hull in UK (SD = 1.2 m), Oost-Zuid-Holland (1.5 m) and Zaanstreek (1.6 m) in the Netherlands. On the other side of the roughness spectrum, the most mountainous areas are the Savoie département in France (SD = 824 m, home to the Mont-Blanc massif), the Torino province in Italy (815 m) and the Valais canton in Switzerland (776 m).

nuts0
Elevation standard deviation of European NUTS0 regions.

As far as whole countries are concerned, the 3 flattest areas are the Netherlands (no kidding), Denmark and Estonia. The 3 hilliest countries are Switzerland, Austria and Liechtenstein (note that Andorra was not included in the analysis).

Finally, the small piece of PyQGIS code I used to compute standard deviation inside polygons:

from qgis.analysis import QgsZonalStatistics

rasterPath = "/path/to/ETOPO.tif"
rLayer = QgsRasterLayer(rasterPath, "DEM")
vLayer = QgsVectorLayer("/path/to/NUTS.shp", "NUTS", "ogr")
if not ( vLayer.isValid() and rLayer.isValid() ):
    print "Error loading layers..."

zonalstats = QgsZonalStatistics(vLayer, rasterPath, '_', 1, QgsZonalStatistics.StDev)
zonalstats.calculateStatistics(None)

print "Done"
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