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Thread: Co-ordinates versus British Grid puzzle

  1. #1

    Join Date
    Feb 2014
    Posts
    3

    Default Co-ordinates versus British Grid puzzle

    We are fairly new to geocaching and bought a Garmin eTrex Summit. We'd like to go paperless by downloading descriptions to our Android phone. Our Summit only seems to function on the British Grid and the geocaching apps don't bring through the British Grid references.

    So I telephoned Garmin telling them that my Summit when set to "Position Format" - hddd.mm.mmmm and "Map Datum" - wgs84 sends me and my family 17 miles in the opposite direction. Whilst the poor Garmin technical bod had me on hold for the third time and was having a nervous breakdown, I changed the "Map Datum" to Ordnance Survey GB. It now seems to work.

    Is the GPS faulty? Do I need to update it? Any clues gratefully received.

  2. #2

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    17 miles out seems an odd value, you don't by any chance live 8.5 miles from the meridian and you've got your E & W mixed up?

    I would be tempted to put it on WGS84 with the hhhh dd.mmm format, and choose a set of co-ords that you know are close to you, create a waypoint with those co-ords in the GPS and then enter the co-ords in exactly the same format into maps.google.co.uk (pay attention to the E/W bit!), then check where google maps puts it, and then go out with your GPS and see if you end up at the same spot.

  3. #3

    Join Date
    May 2004
    Location
    South East Wales
    Posts
    277

    Default

    Have a look at my resource site which explains about the different coordinates and also map datums. It shows what your GPS should be set on (they all work the same way). You can very easily test your GPS. Make sure it is set to Lat/Long HDDD° MM.MMM on the WGS84 map datum. Then go and stand outside your house. Make sure the GPS has got a signal - look on the satellite screen. Then mark your location - create a waypoint. Now, walk down your road for about a quarter of a mile or so. Select the waypoint you created in the GPS and navigate back to your house using the GPS. If it's accurate you should get to within 20 to 30 feet of your front door!
    http://www.follow-the-arrow.co.uk/resources/gps.html

    Chris
    Graculus
    Volunteer UK Reviewer for geocaching.com
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  4. #4

    Join Date
    Feb 2014
    Posts
    3

    Default

    Thank you Martybartfast and Graculus for your replies. I did do exactly what you have both suggested when I first bought the gps. I used google maps to find the co-ords for our local post office just down the road. I calibrated the Garmin, put in the co-ords and it tried to send me several miles in the opposite direction.

    This was several months ago so I shall try it again tomorrow and let you know how I get on.

  5. #5

    Join Date
    May 2004
    Location
    South East Wales
    Posts
    277

    Default

    Have you got the compass arrow screen set to Course pointer or Bearing Pointer? It should be Course. This gives you a simple arrow that points to the waypoint (wherever it is) and you simple walk in that direction.

    Be aware your eTrex only has a GPS compass. This only works when you are moving. If you stop the compass arrow will 'freeze'. If you turn around the arrow turns with you and this could give you a misleading direction. You must be moving.

    Chris
    Graculus
    Volunteer UK Reviewer for geocaching.com
    ----------------------------------------------------------------------------
    UK Geocaching Wiki
    Geocaching.com Help Center
    UK Geocaching Information & Resources website

  6. #6

    Join Date
    Feb 2014
    Posts
    3

    Default

    Thank you Graculus for your help. Our knotty problem has been the GPS has performed perfectly on British Grid but has had a hissy fit on degree and decimal minutes. It tried to send us 19 miles into the North Sea at Felixstowe last weekend. So I swapped the settings to British Grid and it was fine.

    I have done a quick test this morning setting the GPS on hddd.mm.mmmm and wgs84 and it has worked. I need to test it more thoroughly as I don't really trust it. I shall let you know how I get on

  7. #7

    Join Date
    Oct 2005
    Location
    Land of the Bear and Ragged Staff!
    Posts
    843

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    Quote Originally Posted by Templars View Post
    Thank you Graculus for your help. Our knotty problem has been the GPS has performed perfectly on British Grid but has had a hissy fit on degree and decimal minutes. It tried to send us 19 miles into the North Sea at Felixstowe last weekend. So I swapped the settings to British Grid and it was fine.

    I have done a quick test this morning setting the GPS on hddd.mm.mmmm and wgs84 and it has worked. I need to test it more thoroughly as I don't really trust it. I shall let you know how I get on
    In what order are you doing things?
    I seem to remember that if you load caches/coordintes and then change settings for Lat/Long and or Datum, the units can convert what has already been loaded... Thus giving the wrong readings.
    I have a Geocaching problem...
    Work gets in the way!

    * Cache Walker -Caching by byway, not highway! CacheWalker.co.uk
    Walking and Caching in Warwickshire, Worcestershire, Gloucestershire areas

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