Trajectory classification and threshold units

[seth-rees]

I'm working with 12km UKCP18 climate data, which comes in a BNG projection, but I reproject this to WGS84, keeping the 12km resolution. As WGS84 is a coordinate system not a projection system I'm a little confused as to what the units my velocity object would be in, whether it's 12km/year for each cell, or 1km/year as the documentation for gVoCC says it is for unprojected rasters.

Any help would be appreciated, thanks.