Well my immediate test case will be data from an Autocross event. Was even looking to make a personalized print out for a competitor as a trophy from his fast run of day. What I work up would scale to the full circuits as well. @Ulrich_Baer I like your approach. I did a small test with oScad where i fed it an x,y point grid and at each point I placed a verticle cylinder with a z height tied to the reported speed. With some smoothing it had promise if there was a good data set. I’m traveling for work this week, and have a couple layovers, so I’ll be looking at GPS conversion techniques and the oScad programming you pointed out.
I would bet that meshmixer (NOT foss but free) can easily make it thicker without having to learn a new CAD software 
@Jeremie_Francois meshmixer is Autodesk not foss (free yes). Also you assume everybody is familar with meshmixer. So i wonder how you determine what “new” CAD software is for others?
But meshmixer will also work to change the faces of an Object. But for converting GPS coordinates it is not. Or if you download 3D elevation data from google maps.
@Ulrich_Baer ooops right! and I would not be the one to advertise it, sorry (will fix it right now)
Also, right meshmixer is only good to me to tweak/repair/transnform existing STLs which seems to be the case here (now, it can generate some interesting voronoi shapes on its own, but this is another subject).
meshmixer: the deal really is to find a brainless howto, and there are many tutorials to use meshmisher, e.g. https://www.google.fr/search?q=meshmixer+thicken+object&oq=meshmixer+thicken+object
Mastering it is far beyond 95% of its usual users (me included – especially as it used to crash a lot on linux).
https://www.youtube.com/watch?v=sge8029CucM
if you try this with an irregualar looped object (with hole) you often get very weird results.
This is awesome