  The measurement of beam emittances by extracting the quadrupole mode signal
from a 4 plate beam position monitor (BPM) was published at least 40 years ago.
Unfortunately, in practice, this method suffers from poor signal to noise ratio
and requires a lot of tuning to extract out the emittances. In this paper, an
improved method where multiple BPMs are used together with better mathematical
analysis is described. The BPM derived emittances are then compared with those
measured by the Ion Profile Monitor (IPM). Surprisingly, the BPM measured
emittances behave very well and are more realistic than those measured by the
IPM.
