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GPS Coordinates Results

This is a discussion on GPS Coordinates Results within the MapPoint Desktop Discussion forums, part of the Map Forums category; Greetings, I have entered Latitude and Logitude coordinates in MapPoint, which results in an inaccurate location. I also entered the ...

  1. #1
    tommyf is offline tommyf White Belt
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    GPS Coordinates Results

    Greetings,

    I have entered Latitude and Logitude coordinates in MapPoint, which results in an inaccurate location. I also entered the same coordinates into gpsvisualization.com and got accurate results. Is there something I need to do before entering coordinates into MapPoint to achieve correct results? The coordinates I used were:
    Latitude 47.717851
    Longitude -122.404889
    Any help or guidance in the right direction would be greatly appreciated!

    Regards,

    Tommy

  2. #2
    Wilfried is offline Senior Member Black Belt
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    Re: GPS Coordinates Results

    Hi Tommy,

    How innacurate is it ?
    I have many positions very accurate, even on the right side of the street. The coordinates are in degree.

  3. #3
    Winwaed's Avatar
    Winwaed is offline Mapping-Tools.com Black Belt
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    Re: GPS Coordinates Results

    As Wilfried says "how accurate is accurate?" Are we talking the wrong side of the World (in which case a sign is probably wrong) or hundreds of miles (in which case a decimal /minutes of arc conversion if probably wrong), or "hundreds of feet", in which case it is probably a geoid error...

    re. Geoids: MapPoint uses WGS84 - most if not all GPS units will have WGS84 as an option, and it is usually the default.


    Richard
    Winwaed Software Technology LLC
    http://www.winwaed.com
    See http://www.mapping-tools.com for MapPoint Tools

  4. #4
    Wilfried is offline Senior Member Black Belt
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    Re: GPS Coordinates Results

    Hi Richard,

    Thank you for completing my reply
    Can you eventually check the coordinates Tommy gives ? I dont have MP US installed so I cannot check where the coordinates are. But maybe we better wait until he reply ?

  5. #5
    tommyf is offline tommyf White Belt
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    Re: GPS Coordinates Results

    Greetings, and thanks for the responses!

    The coordinates are to a location in Port Orchard, WA, which is accurate in terms of getting the right city. The coordinates come from a vehicle tracking unit which positions every 2 minutes. I entered the coordinates into MapPoint, which resulted in a location 22 miles from Port Orchard.

    Please try entering the coordinates and let me know if you get the same results.

    Thanks for your attention to this post!

    Tommy

  6. #6
    Winwaed's Avatar
    Winwaed is offline Mapping-Tools.com Black Belt
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    Re: GPS Coordinates Results

    The error is at the minutes-of-arc level.
    I tried swapping the DP around (yes I've seen this error before when people write coords down), and that over-corrects to perhaps a 10 mile error in the opposite direction

    My next guess was that the coordinates you have are not decimal degrees, but quoted as degrees, minutes, seconds of arc. Sometimes these are formatted or displayed in a such a way that they are confused for decimal degrees.
    Unfortunately that would give a latitude minutes of arc of 71' - impossible!

    I still suspect the formatting of the frectional degree. Check with the GPS documentation and settings. Make sure you are getting WGS84 coordinates that are displayed as decimal degrees.
    (this error is too big for it to be the geoid error - but you might as well check it at the same time)

    Richard
    Winwaed Software Technology LLC
    http://www.winwaed.com
    See http://www.mapping-tools.com for MapPoint Tools

  7. #7
    Wilfried is offline Senior Member Black Belt
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    Re: GPS Coordinates Results

    Hi,

    If the data comes from a vehicle tracking unit, then the data is possible in identical format as it comes from the GPS receiver. Most (if not all) GPS receivers give their data in NMEA0183 format, wich is ddmm.ffff for latitude and dddmm.ffff for longitude. where:
    dd(d) is the amount of degree
    mm the minutes
    ffff the fractions from the minutes
    So you have to do a little recalculation to get it into floating point degree as MapPoint ask it.

    Can you check the format of the data you get ?

  8. #8
    tommyf is offline tommyf White Belt
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    Re: GPS Coordinates Results

    Greetings,

    I've attached a report, which lists the GPS coordinates I used in Map Point. Let me know what you think...

    Thanks again for your responses!!

    TommyGPS.Data.Info.txt

  9. #9
    Wilfried is offline Senior Member Black Belt
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    Re: GPS Coordinates Results

    Hi Tommy,

    if this is NMEA0183 data then it shoudl be:
    GPSLatitude=4734,7368 -> 47 degree, 34.7368 minutes North
    GPSLongitude=12236,9844 -> 122 degree, 36.9844 West

    For Mappoint convert it to degrees floating point and it shloud be:

    Latitude: 47.57894
    Longitude: -122.6164

  10. #10
    tommyf is offline tommyf White Belt
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    Re: GPS Coordinates Results

    Wilfried,

    Nice work! Could you show me the calculation in which the conversion to degrees floating point was used?

    Thanks for you help!

    Tommy

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