I recently came across a flash where the manufacturer compared their GN to some competitors. I thought that was a smart move as it removes a lot of potential confusion. Still it is interesting to see that GN 110 = GN 60 = GN 34. (and, of course, some of these measurements are in feet and others in metres, which also makes it a little harder to make direct comparisons.)
"Every company measures guide number differently. At LumoPro®, this is how we measure guide number:
GN= Distance x f/stop,
Distance = 10ft, F/stop at 105mm, ISO 100, Full Power = f/11
10ft x f/11 = 110, GN = 110
The LP180's power is roughly equivalent to the Canon Speedlite 600EX-RT or the Nikon SB-900."