TRMM error

["stefano.russo@xxxxxxxx" <stefano.russo@xxxxxxxx>]

Hi,
does anybody know TRMM 3B42 satellite data?
It gives 3-hourly worldwide precipitation data in mm hr^-1 unit.
It also gives the "relative error" associated to the measure.
They say that the "relative error" unit is mm hr-1.
But the "relative error" is not a dimensionless error by definition?
I have this doubt because often the given relative error value is ten 
times or more than the measured value.

On the following link you can find some TRMM specification:
http://disc.gsfc.nasa.gov/precipitation/documentation/TRMM_README/TRMM_3B42_readme.shtml/


Thank you

Stefano