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    Re: UTM question
    From: Greg R_
    Date: 2014 Mar 3, 00:03 -0800

    Hi Paul:
    
    Thanks for the info and the quick reply
    
    >> �why do we need more than 2 northing zones (1 north and 1 south) for the 
    non-polar regions?�
    
    >�We don't. For example, if northing is a big number, you're either in the
    > northern hemisphere and far north, or in the southern hemisphere and
    > near the equator. In practice that's not much ambiguity!�
    
    Correct - much like celestial, where 2 sights will produce 2 points where the circles 
    of position intersect, but you can usually throw out one of them as not 
    likely being a valid position. Though I guess it's always good to define a 
    location without any chance of ambiguity.
    
    >�I suspect these people are using Garmin GPS receivers. None of my
    > Magellans displays the latitudinal zone letter with UTM coords.�
    
    You may be right - I don't have my Garmin that displays UTM (eTrex Legend) handy 
    right now, but if I remember correctly it only displays the letter with the 
    easting coordinate (i.e. the first/top one displayed).
    
    > Another silly Garmin-ism is to show easting and northing coordinates
    > with the same number of digits. But easting is always less than 500 000
    > meters, while northing can be millions. Thus there's always a useless
    > leading zero on easting. It's like displaying degrees of latitude with
    > three digits. The leading digit will always be zero
    
    You're correct on that one, too - if I had to take a guess I'd say they probably 
    include the (superfluous) leading zero just in the interest of "completeness" 
    and so there's no confusion about maybe a digit missing somewhere.
    
    >�Latitudinal zone letters *are* needed in MGRS coordinates, which are
    > based on the same grid as UTM but written in a much different format.
    
    Yep - like you say, that's totally different format altogether - and I guess the 
    answer to my original question isn't to keep UTM and MGRS reasonably similar, either.
    
    
    ________________________________
    From: Paul Hirose 
    To: gregr_ingest---.com 
    Sent: Sunday, March 2, 2014 11:31 PM
    Subject: [NavList] Re: UTM question
    ________________________________
    
    Greg R_ wrote:
    
    > I've been getting up to speed on the UTM grid system, and have a question
    > that I haven't been able to find an answer to: Since the northings are based�
    > relative to the equator, why do we need more than 2 northing zones (1 north�
    > and 1 south) for the non-polar regions?�
    
    We don't. For example, if northing is a big number, you're either in the
    northern hemisphere and far north, or in the southern hemisphere and
    near the equator. In practice that's not much ambiguity! Nevertheless,
    on my scanner I hear search and rescue teams incluing a latitudinal zone
    letter in their UTMs.�
    
    I suspect these people are using Garmin GPS receivers. None of my
    Magellans displays the latitudinal zone letter with UTM coords. If you
    enter a waypoint, they only need you to specify northern or southern
    hemisphere.�
    
    Another silly Garmin-ism is to show easting and northing coordinates
    with the same number of digits. But easting is always less than 500 000
    meters, while northing can be millions. Thus there's always a useless
    leading zero on easting. It's like displaying degrees of latitude with
    three digits. The leading digit will always be zero.�
    
    I know someone who wrote Garmin to point out their illogical UTM format.
    They never responded. To be fair, my info is several years old. I'm not
    familiar with their current receivers.�
    
    Latitudinal zone letters *are* needed in MGRS coordinates, which are
    based on the same grid as UTM but written in a much different format.�
    
    --
    I filter out messages with attachments or HTML.�
    
    View and reply to this message: http://fer3.com/arc/m2.aspx?i=127119
    

       
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