Poster presented at the Sixteenth Biennial
Conference, Society for Marine Mammalogy,
San Diego, CA, December 2005
Using
compass and reticle binoculars to measure animal position: An
evaluation and comparison to theodolite data
Suzanne
Yin1,
Adam S. Frankel1,2,
Christine M. Gabriele1,
and
Susan H. Rickards1
1Hawai‘i
Marine Mammal Consortium
P.O. Box 6107
Kamuela, HI 96743
2Marine
Acoustics, Inc. 706 Giddings Ave Suite 1C Annapolis, MD
21401
Shore-based
theodolite tracking of coastal cetaceans is a useful and
widespread technique that is not always feasible due to expense,
geography, the experience-level of observers or other issues. We tested
the feasibility of using reticle binoculars to replace or supplement
theodolite tracking for determining whale and vessel locations from a
shore based observation site with known elevation above sea
level. We compared the accuracy and precision of (n= 278)
binocular versus theodolite fixes of 2003 and 2004 humpback whales off
the island of Hawai‘i, collected during scan samples. Theodolite
positions are recorded in azimuth and declination and then converted
into x/y coordinates. Reticle binoculars allow users to report azimuth
and declination from the horizon. Both methodologies allow calculation
of distance, dependent on a known elevation above sea level. We found
close agreement between distances towhales obtained from binocular and
theodolite fixes when measured reticles >1. A linear regression of
binocular reticle distance on theodolite distance was significant
(F(1,276) = 5120, p<0.00001, r2
= 0.948). A similar regression of binocular bearing on theodolite
bearing was even more predictive (F(1,275) = 26619, p < 0.0001, r2
=0.989). Binocular measurement distance error increased greatly
when measurements with reticles <1 were used (i.e. closer to the
horizon). Marine binoculars with compass bearings and reticles
cost less than a theodolite, are very portable and have a wider field
of view than theodolites. Tracking animals with binoculars also
requires less training and can be used by several observers at the same
shore station. Locations derived from marine binoculars may be
less precise, and may not be suitable for distant or detailed tracking,
but this technique opens the possibility of measuring animal locations
to a greater range of observers (e.g. schools and citizen science
groups).
