Various tools and script to manipulate DEMs.
Believe it or not, Opensnowmap.org hillshade and contour lines
were made from these.
However, they are not clean, nor cleaned, nor will be. Usually the 
script were fixed when the calculations had run for weeks and gave
a bad looking result or a disk / memory full exception.
The author usually try to fix, then run again and came back a few
week later to see if the script end up with something useable.
When the result was good enough, the tools were forgotten and never
looked at again. Likely, this is not the last working version 
you'll find here.
I am however glad to answer any question you could have about your 
own issues in relief maps with GDAL. 

In fact, all you probably need is GDAL (www.gdal.org).