[Inkscape-user] map units

Hello,

I'd like to draw the map of a building using inkscape, and overlay my drawings with satellite views.

A batch program would then modify the map to adjust the position of some points.

Then I would like to import the svg file into sketchup and use it as a basis for quick 3d renderings.

And now the question: which units should I use for the canvas?

The building size is 50x15 meters. My first idea was to use this size as the canvas, but for some reason, in such a case, inkscape does not allow me to unzoom as much as I would like too (I cannot have the full drawing on screen).

Is there as reson for this and a workaround?

I know many maps and GIS use SVG somehow, how do they choose their basis unit? A Cheers