@gaieus said:

Hi José,
(and this is my answer to your original post which I don't know where disappeared)

@unknownuser said:

The solution has a couple of steps at this stage of modelling...
Also, many depends on the purpose of your modelling; is it for Google Earth or just for other purposes?

First of all, make sure that the geometry of the individual buildings are grouped (or made as a component). This way you can move them separately easily.
As far as I can see from your screenshots, you have already imported the GE Snapshot 8and terrain also in this case). If you toggle the terrain layer, it will display the non-planar terrain as it can be seen in GE.
Now comes your answer - whether it is going to be for GE or not as the strategy will differ.

Could you please, attach your images straight to the post (there is an attachment tab below where you type) as ImageShack is very slow for many people here (and only gives a very small, embedded and resized image even if clicked on).

Well, if you imported the GE snapshot (for geolocatin and to get some terrain), all you need to do is to edit the terrain to match your schools real terrain.

If you activate the Google toolbar (View menu > toolbars), there is a "toggle terrain" button. it will turn the GE snapshot layer off and the GE Terrain layer on (and vice versa). You can do this manually in your Layers dialog, too (Window menu...)

Now once you have the non-planar terrain active, you will notice that even that is not really following the actual terrain of your school (its resolution is most probably not as detailed as in real life). You can edit this terrain however with the sandbox tools (if you have not activated them under Window > preferences > extensions, do so now and activate the toolbar suggested above).

When you first click on the terrain group, you will see that it has a red bounding box (by default). It means that it is locked to prevent unwanted changes. Right click and "Unlock" it. Now the bounding box is blue (by default) and if you double click on this group, you can edit the terrain with the sandbox tools. You can use the stamp tool to "stamp" the footprints of your buildings into it (which will always result in a flat, horizontal "platform" with some given, slanting "skirt" around - exactly what you seem to need).

See what the help center is saying about the stamp tool:
http://sketchup.google.com/support/bin/answer.py?answer=95061
Where you nee more details in your terrain, you can add detail as well to make it smoother:
http://sketchup.google.com/support/bin/answer.py?answer=95042

Hello Csaba Pozsárkó,
Thanks a lot for your reply once again.
Somehow I find this tool very hard to work with, and it seems that the school model will stay the same, unfortunately.
Anyway, thank's a lot for your help.