Any advantage of the DMS system over the Decimal Degree?

Discussion in 'General GPS Discussion' started by qquito, Jan 14, 2011.

  1. qquito

    qquito Guest

    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

    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!

    qquito, Jan 14, 2011
  2. 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.
    John Tserkezis, Jan 15, 2011
  3. qquito

    Peter Guest

    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.
    Peter, Jan 15, 2011
  4. 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

    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 Michna, Jan 15, 2011
  5. qquito

    Wayne R. Guest

    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?
    Wayne R., Jan 16, 2011
  6. qquito

    qquito Guest

    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.

    qquito, Jan 16, 2011
  7. qquito

    Jack Simms Guest

    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

    Jack Simms, Jan 16, 2011
  8. qquito

    rick Guest

    rick, Jan 16, 2011
  9. qquito

    rick Guest

    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, Jan 16, 2011
  10. 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.
    John Tserkezis, Jan 17, 2011
  11. qquito

    DonH Guest

    # 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
    Why then the need of Decimal, if appropriate maths can be
    DonH, Jan 19, 2011
  12. qquito

    Rod Speed Guest

    Because it can be more convenient to use.
    Rod Speed, Jan 19, 2011
  13. LOL - Actually I just thought of Roman figures. :)-)

    Hans-Georg Michna, Jan 20, 2011
  14. qquito

    UGL Guest

    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.
    UGL, Jan 24, 2011
  15. qquito

    qquito Guest

    Thank you very much! It helps to explain the reason for the
    persistence of Degree-Minute-Second system. --Roland
    qquito, Jan 25, 2011
  16. qquito

    Jim Lux Guest

    Or as my daughters would say in elementary school math class

    Curse those Babylonians and their Base 60 numbering system.
    Jim Lux, Jan 25, 2011
  17. That's hair-raising!

    Hans-Georg Michna, Jan 26, 2011
  18. qquito

    Geo Guest

    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
    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

    Specifying the location by post code gives the correct information
    < >
    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...
    Geo, Jan 27, 2011
  19. qquito

    Jack Simms Guest

    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
    Jack Simms, Jan 28, 2011
  20. qquito

    Geo Guest

    Every airfield has a reference point which is shown on the charts.
    Geo, Jan 28, 2011
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