[Qgis-user] Need help: what is the measurement unit of interval X, Y in print composer - map grid?

[Cao Minh Tu]

Dear all,

I want to put a grid overlay on my printed map with lines 20 meters 
apart, I managed to display a grid in print composer but now I don't 
know what value to put in Interval X, Y to realize what I want because I 
don't know their measurement unit.

Anyone can help me on this?

Thanks a lot.