Reducing terrain mesh memory size on disk

Hello,
For a simulator i’m wondering how i can get the lowest memory size of a terrain mesh as possible.
My actual workflow:
1 creating from maps a cleanedup svg (scalable vector graphic)
2 import the svg in blender
3 in object mode go to convert the curve into a mesh
4 extrude the mesh and give material to it

Any sugestions to help me?
thx,
RobMitch