On Fri, 14 Jan 2011 14:39:27 -0800 (PST), qquito wrote:
>The Degree-Minute-Second (DMS) system is widely used in geographic
>coordinates in many places. Google Earth and Wikipedia (in entries of
>places) are just two ready examples. However, it is pretty much
>annoying to make notes of the latitude and longitude of a place in the
>DMS system or to copy/paste them for various purposes. And when you
>use the latitude and longitude as inputs for some kind of
>trigonometric computation, you need to convert them to decimal
>degrees.
>
>So I am wondering if the DMS system has real advantages over the
>decimal degree in today's world. Who are the people that would prefer
>the DMS system to the latter?
Older people? Degrees, minutes, and seconds were almost
exclusively used 50 or more years ago.
And, no doubt, a mathematician would always prefer degrees with
decimal degrees for its purity, clarity, and simplicity.
But to complicate matters, the default today is neither; it is
degrees and minutes with decimal minutes. The reason is quite
rational---this enables you to determine coordinates from maps
more easily.
The reason for this, in turn, is that on a meridian (and along
the equator) one minute is one nautical mile, so, for example,
to travel 27.5 degrees north, you have to travel 27.5 nautical
miles north.
That is why maps, particularly modern, GPS-friendly ones, show
minutes, and that is why you are best off, when calling an
emergency help vehicle, dictating your position in degrees and
minutes with decimal minutes, like this:
"North fourty-eight degrees, three decimal seven eight minutes,
east eleven degrees, fourty-one decimal six seven minutes"
(For precision to a few meters you want three decimals, not
two.)
Of course, anyone well trained in emergency or search and rescue
operations will be able to take coordinates in any of the three
common formats. So if you need help very urgently and have your
GPS set to the "wrong" format, read it out anyway and ask if it
is understood. On the other hand it cannot hurt having your GPS
set to the default format of ddd mm.mmm as a precaution.
Hans-Georg
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