Which albedo data should I use, measurements from a POA sensor or a Horizontal sensor?

[Venicios Andrade]

I have irradiance data for albedo calculation measured in the field, both with sensors installed horizontally and with sensors installed in the POA. I would like to know which data I should consider, Horizontal or POA, to define the albedo for the bifacial evaluation. 

Also, what data should I extract to compare with the data collected by the horizontal sensor facing the ground and what data for the POA pyranometer facing the ground? Would it be the GlobGnd variable or a difference between GlobGnd and ReflLss?