R GIS: Terrain Analysis for Polygons as Simple as it Gets!

library(rgdal)
library(raster)

alt <- getData('alt', country = "AT")
gadm <- getData('GADM', country = "AT", level = 2)
gadm_sub <- gadm[sample(1:length(gadm), 5), ]

plot(alt)
plot(gadm_sub, add=T)

asp <- terrain(alt, opt = "aspect", unit = "degrees", df = F)
slo <- terrain(alt, opt = "slope", unit = "degrees", df = F)

> extract(slo, gadm_sub, fun = mean, na.rm = T, small = T, df = T)
  ID     slope
1  1  9.959053
2  2  1.047443
3  3  7.456165
4  4  1.673786
5  5 11.946553

> extract(asp, gadm_sub, fun = mean, na.rm = T, small = T, df = T)
  ID   aspect
1  1 170.8065
2  2 184.0130
3  3 190.7155
4  4 136.8953
5  5 205.2115

Use R to Bulk-Download Digital Elevation Data with 1" Resolution

Here's a little r-script to convenientely download high quality digital elevation data, i.e. for the Alps, from HERE:

require(XML)

dir.create("D:/GIS_DataBase/DEM/")
setwd("D:/GIS_DataBase/DEM/")

doc <- htmlParse("http://www.viewfinderpanoramas.org/dem3.html#alps")
urls <- paste0("http://www.viewfinderpanoramas.org", xpathSApply(doc,'//*/a[contains(@href,"/dem1/N4")]/@href'))
names <- gsub(".*dem1/(\\w+\\.zip)", "\\1", urls)

for (i in 1:length(urls)) download.file(urls[i], names[i]) 

# unzip all files in dir and delete them afterwards
sapply(list.files(pattern = "*.zip"), unzip)
unlink(list.files(pattern = "*.zip"))

p.s.: Also check raster::getData which pulls SRTM data at 90m resolution for a location / region!

QGIS: Curing Small Aesthetical Flaw

Procrastination ahead! ..When starting QGIS, does the popping up of the cmd prompt window also annoy you like me? If you want to solve this, put the below vbs script in your PATH/bin folder (or anywhere else, if you wish).

Check the path to qgis.bat in the script and change it if yours is different. Then, go to the QGIS-Desktop shortcut and in the options dialogue point to the vbs script as target. Your done - no more popping cmd windows when starting QGIS!

Set WshShell = CreateObject("WScript.Shell")
WshShell.Run chr(34) & "C:\OSGeo4W\bin\qgis.bat" & Chr(34), 0
Set WshShell = Nothing