Measuring HPBW from gran gain radiation pattern plot

Hello

Its a simple question however i don't see this in any books but i see it on papers, can i measure 3dB Half power beam width from gain pattern? if so, do i have to normalize it, or can i just subtract 3dB form the highest gain (in a given direction) and measured the beam width from there.

Yes, just measure the width of the two points that are 3 dB down from the maximum, normalization is not necessary.