The Accuracy Of Satellite Navigation

Discussion in 'GPS / Geocaching & Mapping Applications' started by themanfromvan, Dec 4, 2009.

  1. themanfromvan

    themanfromvan Van, PA - Near The PA Wilds

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    I have a Magellan eXplorist 210, one of the first hand held GPS units ever made. My question to all of you is, do you find discrepancies in GPS information from one application to another?

    The reason I ask is because I have taken waypoints stored in my GPS and applied them to Google Earth and in every case, it puts me in an area not even remotely close to where the co-ordinates were marked. I have obtained these waypoints by standing and marking them myself, in my GPS unit.

    Now, to me, I would reason that Google Earth would be the most accurate because it is using the newest technology. However, the killer to that theory is that when I give people waypoints to navigate to certain areas (like my own hidden geocache), they are able to find the place or object from the information obtained through my GPS.

    So, which is accurate? The 8-9 year old GPS or Google Earth? Anyone else have any experience, information or theories on the matter?
     
  2. samtgrizz

    samtgrizz New Member

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    The following might explain the difference.

    When building whole-earth databases, a single global projection is the most convenient to use. Google Earth uses Simple Cylindrical projection for its imagery base because. This is a simple map projection where the meridians and parallels are equidistance, straight lines, with the two sets crossing at right angles. This projection is also known as Lat/Lon WGS84.
     
  3. stefbauer

    stefbauer New Member

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    On May 2, 2000, at approximately midnight, eastern savings time, the great blue switch controlling selective availability was pressed. Twenty-four satellites around the globe processed their new orders, and instantly the accuracy of GPS technology improved tenfold. Tens of thousands of GPS receivers around the world had an instant upgrade

    www.geocaching.com has a bunch of info.... as well as info in different GPS's

    I agree with the prior post about google-earth, however, I think you are also fighting with (in technology terms) something that is about 15-20 years old.... technology improvements especially since the changes to allow increased accuracy in 2000 have been geometric. The accuracy of the new recievers (even cheap ones) will surprise you, espcially relative to a older unit (I have a Garmin etrex... and it is nowhere as accurate as other units I have compared it to that are newer).


    It goes to the questions.... how close do you need to be.... 10ft, or 75+-. If your trying to get back to your car at the trail-head... 75 feet is plenty close. Trying to find a micro geocache in the woods, you might be frustrated.
     
  4. themanfromvan

    themanfromvan Van, PA - Near The PA Wilds

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    I am not particularly concerned about accuracy. I just wondered why the discrepancy in location using the same waypoints. Now I know !!

    I figured Google Earth would be more accurate, but I guess I'm wrong. I know how accurate GPS can be because we have a Garmin unit at work and that baby will take me right to someone's house. Wait - I should say that 90% of the time, it comes through for me. But, that one time in ten? Holy smokes has it taken on some wild journeys.

    Okay, I'll continue to trust the information provided to me by my old, freebie GPS. Thanks !!
     
  5. phipps

    phipps Member

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    The other possibility is the format you're using. Your GPS might be in one format and Google Earth is needing a different format.
     
  6. Snow

    Snow Well-Known Member

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    I like the driving directions to London, England provided by Google . [:D]
     
  7. silvermickey2002

    silvermickey2002 Morris County, NJ

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    When using the GPS for driving directions make sure you look at maps before you go on a trip. A buddy of mine used it to meet us at a state forest he never went to and his GPS was more than 2-3 miles off!
    I now have an iPhone with AT&T Navigator app and I'm finding it to be pretty accurate, but I will always refer to a map just to get an idea where I am going. Do not put all your trust in your GPS.

    That good ole road atlas still works and does not need to be charged before a trip!!

    Response from Google:
    We could not calculate directions between Denville, NJ and London, England.
     

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