Why is there noise in my output? Ive only been introduced to Blender yesterday and have been trawling through the tutorials and loving it, definitely a new fan, albeit still taking very small steps.

I exported a VRML from a GIS application (ArcScene).  I have done little to the scene in Blender, apart from adding some material effects to the ground layer.

What I can't understand is why my final render has a lot of noise in it.

Can someone give me some pointers on how to get a better quality render?  Is it something to do with the render settings or have I missed something on the import/configuration of the scene?
Blender Internal

If you're using Blender Internal with Raytracing as your Gather mode, the following will work. Raytracing is realistic, but it requires a certain number of samples, otherwise it will be grainy.

In the World settings in the Gather section, change the samples to something like 10 or 12:


Cycles

If you're using Cycles, you can turn up the render samples in the Render panel under sampling: