Any advantage of the DMS system over the Decimal Degree?

Hello, All:

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?

Thank you for reading!

--Roland

 

Personally, I prefer decimal degrees over DMS simply because there's
less cutting and pasting to do. If I have that luxury of course.

For the end user, I really can't see any advantage over any other,
other than perhaps if they had one device or software interface that had
limited decimal resolution, where the DMS option may offer a higher
location resolution. But that's just a software limitation.

Past that point though, there would be little to argue about regarding
advantage, mainly because all my devices and applications can cater for
pretty much anything.

From a data supplier perspective, one could speculate that database
might be smaller, or easier to deal with if they stored locations in one
format over another. But even that would be a rather weak argument.


Perhaps it would be more important to state a device, software or other
interface *should* offer all the format variations for convenience,
rather than for any particular technical advantage.

 

and what about hybrid notation, my Nokia displays lat & long as
degrees'minutes'seconds.decimal-seconds ie 52'24'32.45
really it doesn't matter as long as every application you use can be set
to the same format.

 

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

 

I think the only time DMS would appeal to any real world user would be
when trying to transfer coordinates verbally, perhaps over a radio
link - only because the extra words involved (the D, M & S) set a
sequence that numbers alone won't.

It's tough being confident that an error didn't creep into any verbal
handoff of coordinates, and numbers-only seems like the most
error-prone to me.

Isn't DMS probably nothing more than a legacy of transits & sextants?

 

I am also curious if it is used today merely because it is a legacy
from the past even though it has no perceived advantage but only
inconveniences today's users.

---Roland

 

Actually, there is a very real advantage to the use of DD MM SS when
working with position/distance

1 minute of longitude at the equator, or latitude, is a distance
measurement of 1 NM (nautical mile)

And surely it is obvious that fixing a point to 1/60th of NM is much
more precise than fixing point to 1/10th NM

Regards

 

If you haven't looked at the UTM system you should. It is much more
accurate, does not have to be converted, easier to communicate and
works with almost everything. It is worth considering it also has a
very small learning curve.
My opinion,
Rick

 

UTM is useful if you're working with maps, and a standard ruler or
length measuring device.

Any ruler distance in any axis on the map, will scale correctly to any
real-life distance on the earth's surface. Especially useful when
you're dealing with hiking maps.

However, UTM is only suitable for smaller scale maps, otherwise you
start to see image "stretching" to fit a spherical surface onto a flat
piece of paper.
Also, it is not aesthetically "neat" over zones, (degree lines) so the
easting and northing lines will appear "tilted" at these borders.


Also, I dispute your claim that it is "more accurate". There is no
reason that the UTM projection has particular ability to offer higher
accuracy or resolution than any other projection.

 

# I assume the DMS system you refer to is of the pseudo-decimal notation,
similar to BCD (binary coded decimal), whereby numbers are merely placed in
sequence, irrespective of actual maths.
The full DMS system of degrees, minutes, and seconds, has each being a
60th of the higher value, and decimal equivalent - of minutes and seconds -
is merely used for convenience of calculation.
It may be possible to convert them all into Base 60, and use that? As
with hexadecimal, octal, binary, etc. Then any "decimal" presentation would
comply with the rules for column switch, across from right to left.
We've become so used to Decimal that Base 10 comes naturally, even if
originated from us having ten fingers(toes).
Actually, Base 60 would amount to the same as exists at present, except
that two columns are used, instead of unity substitutes, as A-F in
Hexadecimal.
Why then the need of Decimal, if appropriate maths can be
applied/devised?

 

Because it can be more convenient to use.

 

LOL - Actually I just thought of Roman figures. -)

Hans-Georg

 

The degrees-minutes-seconds system for angles is, like hours-minutes-
seconds of time, a sexagecimal system and has been around (excuse the
pun) for a very long time.

It is used extensively, not only in navigation and positioning for
geographical coordinates, but also by land surveyors for field angle
measurement and for azimuth/bearing display.

While some software may expect decimal degrees, many programs expect
DMS values, but in a decimal format. That is, an angle of say
12°13'14" is expected to be input as 12.1314, to make data entry
easier (stay on the number keypad). So don't assume that when you see
what appears to be decimal degrees input that it is actually decimal
degrees in meaning, unless you're sure!

I wouldn't necessarily agree with Peter that 52'24'32.45" represents a
hybrid notation; it is just part of the same DMS system, since seconds
are not usually subdivided in any other way except decimally. There
are, however, slightly more hybrid notations out there, especially in
GIS/GPS, that use degrees and decimal minutes (no seconds). Thus
12°13'40" is represented as 12°13.667'

Will we ever likely see the demise of DMS? No. Surveyors are a rather
conservative lot ("the oldest profession" and all that) and are very
happy with DMS. Even though, as a programmer (of Copan -- a free CoGo
program for surveyors) i must say it would be a lot easier to deal
with just decimal degrees. Ask yourself, Will we ever see decimal
hours instead of the clumsy old hours-minutes-seconds?

Actually, there is a system of decimal degrees in surveying -- it's
called gons or grads, but there are 400 of them in a circle! It's
popular in parts of Europe.

 

Thank you very much! It helps to explain the reason for the
persistence of Degree-Minute-Second system. --Roland

 

Or as my daughters would say in elementary school math class

Curse those Babylonians and their Base 60 numbering system.

 

That's hair-raising!

Hans-Georg

 

I found out the hard way that web databases can be similarly wrong e.g.
in Scotland, Edinburgh Airport is here:-
55°57'0" N, 3°22'21" W
55.95, -3.3725
Elevation 33 feet
ICAO code EGPH

One (of many) web sites that attempt to provide weather information by location
is:-
<http://www.metcheck.com/V40/UK/FREE/tomorrow.asp?zipcode=egph>
gives this information which you will note has expressed the known LAT and LON
in degrees:-
Lat : 55.6N Lon : 3.2W ASL : 605m

and the weather is of course slightly different that further South and up a
hill!

Specifying the location by post code gives the correct information
<http://www.metcheck.com/V40/UK/FREE/today.asp?zipcode=eh129dn >
EH12 9DN
Lat : 55.9N Lon : 3.3W ASL : 11m

The web site owner simply shrugs it off as that was the data in the database
they purchased...

 

Which part of the airport is at that position ???

A major airport would likely span at least 0.3 degrees, especially
sited at a latitude near 60 degrees. AT that latitude, a distance on
ground of 2 miles would equate to around 2.6 degrees longitude

 

Every airfield has a reference point which is shown on the charts.