RSAGA: Getting Started

RSAGA provides access to geocomputation capabilities of SAGA GIS from within R environment. Having SAGA GIS installed is a (quite obvious) pre-requirement to use RSAGA. 

In Linux x64 sometimes additional preparations are needed. In Linux SAGA as well as other software that would like to use SAGA modules usually searches for  them in /usr/lib/saga, but if your Linux is x64, they usually will be located in /usr/lib64/saga. Of course you may set up proper environmental variables, but the most lazy and overall-effective way is just to add symbolic link to /usr/lib64/saga (or whatever a correct path is) from /usr/lib/saga:

:~> sudo ln -s /usr/lib64/saga /usr/lib/saga
Now no app should miss these modules.

DSM to DEM Conversion

Often you may have some Digital Surface Model (DSM) acquired from a LiDAR data, and you may desire to get rid of buildings and trees in order to get a DEM. There can be found some articles on a subject that would provide more accurate result then that described here. But I will show here my quick-n-dirty way when one don't need extreme accuracy. It is meant to be used for a relatively flat urban areas.

There will be 3 steps:

1. Subtraction of the elevated objects like buildings and trees from DSM.
2. Filling the gaps of the raster cleaned of the elevated objects.
3. Polishing the DEM.

FOSS software you will need: SAGA GIS, QGIS.

Initial DSM (LiDAR)