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Question about Datums

rochrunner 88 Points
edited November -1 in GPS Discussions
I am not very familiar with the different GPS "datums" that are or have been in common use, but am wondering if it has something to do with a recent issue I've had.

I marked some locations of personal interest 15+ years ago using an older-model GPS (either a Garmin III+ or V). These points showed up accurately in Garmin's Mapsource of that era, as well as some other programs such as Delorme Street Atlas & Topo.

I recently used an Android smartphone application that displays these points on a map by basically throwing the coordinates over to the Google Maps application. To my surprise, the points shown on the map were noticeably well off from their correct locations.

I'm pretty sure the data was converted correctly when entered into the program I'm using. Could this be caused by the use of a different datum between the old Garmin and Google Maps? And how far off would the difference typically be (I'm seeing points off by several miles!).

Comments

  • zee 97 Points
    From a location in E Kansas, I made a WGS 84 waypoint, then made several more using different Datums, with the same L/L numbers.
    The Measure Distance tool, on my Garmin 60Cx Map Page, shows that the distance from the WGS 84 point to the:
    WGS 72 is 14 ft
    NAD 27 CONUS is 71 ft
    NAD 83 is about 3 ft E and 3 ft S ((from a MobileMapper)

    I don't have a smart phone to compare.
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