Maser Source Finding Methods in HOPS
  The {\bf H}$_2${\bf O} Southern Galactic {\bf P}lane {\bf S}urvey (HOPS) has
observed 100 square degrees of the Galactic plane, using the Mopra radio
telescope to search for emission from multiple spectral lines in the 12\,mm
band (19.5\,--\,27.5\,GHz). Perhaps the most important of these spectral lines
is the 22.2\,GHz water maser transition. We describe the methods used to
identify water maser candidates and subsequent confirmation of the sources. Our
methods involve a simple determination of likely candidates by searching peak
emission maps, utilising the intrinsic nature of water maser emission -
spatially unresolved and spectrally narrow-lined. We estimate completeness
limits and compare our method with results from the {\sc Duchamp} source
finder. We find that the two methods perform similarly. We conclude that the
similarity in performance is due to the intrinsic limitation of the noise
characteristics of the data. The advantages of our method are that it is
slightly more efficient in eliminating spurious detections and is simple to
implement. The disadvantage is that it is a manual method of finding sources
and so is not practical on datasets much larger than HOPS, or for datasets with
extended emission that needs to be characterised. We outline a two-stage method
for the most efficient means of finding masers, using {\sc Duchamp}.
