satellite tags

From: Pieter Arend Folkens (
Date: Sun Nov 18 2001 - 23:29:54 EST

>why use satellite tags?
>why use satellie tage with wales or marine animals?
>are satellite positions always accurate?why or why not?

Satellite tags are one of a wide varitey of devises/techniques for
acquiring data on free-ranging biological subjects. It just so
happens that these tags also provide accurate information and remote
sensing, that is, the data collector does not affect the
behavior/movement of the subject.

Satellite tags are particularly useful on marine mammals because of
the inherent difficulty in tracking these critters by other means.
Since whales live mostly underwater and surface only occasionally,
data collecting from ships automatically has a risk of affecting the
data because of the noise an ocean-going vessel produces. Applying
the Heisenberg Uncertainty Principle to biology, the presence of the
observer means one cannot be absolute certain of the accuracy of the
data. Satellite tags overcome much of this.

Positions given by satellites are amazingly accurate thanks to
mathematics, trigonometry to be exact. Triangulation is used for
positions, so no matter what relative angles three objects are to
each other, trig functions and time give us precise location.

Data is generally so accurate, that if data received is not
consistent with what is anticipated, a closer look often reveals
surprising discoveries. For example, a satellite tag on a southern
elephant seal several years ago provided data of dive depths that
exceeded the known bathymetric depth of the ocean in that area by
many meters. The scientists thought their gear was malfunctioning or
not properly calibrated, posing a possible threat that all their data
was inaccurate. Closer inspection showed that the data was indeed
very accurate. The seal had found a 50 meter deep hole at the bottom
of the ocean, in which it repeatedly found its preferred prey items.


Pieter Folkens

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