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  • Coordinates not understood

    Hello house.
    I want to trace a lost old property through its survey drawing that I just discovered. These are the coordinates I saw on its 2 axis:
    351 633.455mN
    96 172.723mE
    My challenge is how to convert these indicators to the DMS, DMM or DD formats which I am more attuned to.
    Your assistance will be highly appreciated. Thanks.

  • #2
    Originally posted by Ashiwaju View Post
    Hello house.
    I want to trace a lost old property through its survey drawing that I just discovered. These are the coordinates I saw on its 2 axis:
    351 633.455mN
    96 172.723mE
    My challenge is how to convert these indicators to the DMS, DMM or DD formats which I am more attuned to.
    Your assistance will be highly appreciated. Thanks.
    I can't tell whether those are UTM or MGRS (USNG?) coordinates, or a grid system I am not familiar with. Is it possible you have the northing and easting reversed?

    UTM coordinates divide the world into 60 wedges that are 6 of longitude wide, centered on the odd multiples of 3. The central meridian has a false easting of 500 000 m. A rectangular grid is imposed, measuring meters east or west of the central meridian. In the northern hemisphere, the northing is meters north of the equator, in the southern hemisphere, a false northing is added so the equator is 10 million meters. Because the zone is only 3 wide, eastings smaller than than 166 000 m are not possible.

    MGRS (Military Grid Reference System), or USNG which is similar, divides the UTM wedge into 100 km squares and measures northing and easting in meters from the southwest corner. Northing in excess of 100 000 m is not possible. The square designator is required since it "conceals" the most significant digits of the UTM coordinates

    If it is UTM, you need to know which UTM zone and whether north or south of the equator. If MGRS, you need that UTM zone, latitude band, and square designator. Those can all be determined from any location hint (city) that gives approximate latitude and longitude. However, the coordinates you gave appear to violate the standards for UTM or MGRS, so unless there is an error (reversed?), I don't know what grid system is being used.

    Many countries (and US States) have their own local grid system to impose rectangular coordinates over their little bit of round earth. If you know approximate location to national and local government level, it may be possible to guess what rectangular coordinate system and research the transformation to lat/long or find a GPS which can work directly in that coordinate system.

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    • #3
      Thanks a lot for your illuminating response.
      I quoted directly from the markings on the survey papers I discovered...so if there were any errors, it would have emernated from the surveyors (which is unlikely).
      Further markings from the survey paper, which may be useful for unraveling this challenge are as follows:

      "Lay-out off Aiyetoro Road, Abeokuta, Ogun State, (Nigeria)"
      "Origin :- N. N. O."
      Survey was registered on 10th September, 1979.

      Hoping this further information may make a difference. My gratitude.

      Comment


      • #4
        Originally posted by Ashiwaju View Post
        Thanks a lot for your illuminating response.
        I quoted directly from the markings on the survey papers I discovered...so if there were any errors, it would have emernated from the surveyors (which is unlikely).
        Further markings from the survey paper, which may be useful for unraveling this challenge are as follows:

        "Lay-out off Aiyetoro Road, Abeokuta, Ogun State, (Nigeria)"
        "Origin :- N. N. O."
        Survey was registered on 10th September, 1979.

        Hoping this further information may make a difference. My gratitude.
        Thank you. That is a help. Please understand that all I know about Nigerian grid coordinates is what I am finding on Google. Nigeria is divided into three modified Transverse Mercator Zones and those are valid coordinates in the the "Minna West Belt" zone in the southwest corner of the country:
        https://i.stack.imgur.com/SiIeq.png

        I am now searching for a converter and will add to this response if I find one.

        Edit: Found a converter. Other Google articles indicate there are unknown issues in the conversion of the Minna West grid to world datums so there may be accuracy issues.

        Converter link: https://epsg.io/transform#s_srs=2639...351633.4550000

        Result 316'50.532" E, 710'46.717" N

        On a world map it is slightly south of the rotary intersection of numbered roads F200 and F102, west of Abeokuta, so it is at least in the ballpark. Hope this helps.
        Last edited by JohnS; 08-04-2019, 04:40 AM.

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        • #5
          Wow! JohnS. I must thank you a zillion times, because am reasonably certain that you've helped to locate the missing property which I wasn't certain I'd ever locate due to its strange reference coordinates.
          I already have a mental picture of its whereabouts now, and must proceed to the field asap to do a physical search, and verify.
          Once again, my eternal gratitude.

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