Re: Find nearest geographic coordinates

Thanks for your help guys.

/Frank

Mon 30 nov. 2020  04:07, Anders Dahlin <[email protected]> wrote :

> I don't know how well this will suite your needs, but it's what I use to
> calculate the distance between to {Lat, Lng} points.
>
> -define(EarthRadius, 6372.8).
>
> haversine({Lat1, Lng1}, {Lat2, Lng2}) ->
>     RLat1 = deg2rad(Lat1),
>     RLat2 = deg2rad(Lat2),
>     DLat  = RLat2 - RLat1,
>     DLng  = deg2rad(Lng2) - deg2rad(Lng1),
>     A     = math:pow(math:sin(DLat/2), 2) +
>             math:pow(math:sin(DLng/2), 2) * math:cos(RLat1) *
> math:cos(RLat2),
>     C     = 2 * math:asin(math:sqrt(A)),
>     ?EarthRadius * C.
>
> deg2rad(Deg) ->
>     math:pi() * Deg / 180.
>
>
> On 2020-11-28 20:09, Joa Gre wrote:
> > This might come in handy:
> >
> > %%
> https://en.m.wikipedia.org/wiki/Geographic_coordinate_conversion#From_geodetic_to_ECEF_coordinates
> <
> https://en.m.wikipedia.org/wiki/Geographic_coordinate_conversion#From_geodetic_to_ECEF_coordinates>
>
> > %%
> https://en.m.wikipedia.org/wiki/Geodetic_datum#World_Geodetic_System_1984_(WGS_84)
> <
> https://en.m.wikipedia.org/wiki/Geodetic_datum#World_Geodetic_System_1984_(WGS_84)
> >
> >
> > geodetic_to_ecef_coordinates(Latitude, Longitude, H) ->
> >     CLatitude = math:cos(Latitude * ?RADIANS_PER_DEGREE),
> >     SLatitude = math:sin(Latitude *  ?RADIANS_PER_DEGREE),
> >     CLongitude = math:cos(Longitude * ?RADIANS_PER_DEGREE),
> >     SLongitude = math:sin(Longitude  * ?RADIANS_PER_DEGREE),
> >     %% Semi-major axis
> >     A = 6378137.0,
> >     A2 = math:pow(A, 2),
> >     %% Semi-minor axis
> >     B = 6356752.3142,
> >     B2 = math:pow(B, 2),
> >     %% Prime vertical radius of curvature
> >     N = A2 / math:sqrt(
> >                math:pow(CLatitude, 2) * A2 + math:pow(SLatitude, 2) *
> B2),
> >     X = (N + H) * CLatitude * CLongitude,
> >     Y = (N + H) * CLatitude * SLongitude,
> >     Z  = (B2 / A2 * N + H) * SLatitude,
> >     {X, Y, Z}.
> >
> >
> > Den ons 25 nov. 2020 22:39Frank Muller <[email protected]
> > <mailto:[email protected]>> skrev:
> >
> >     Hi guys,
> >
> >     I've a list of geographic coordinates:
> >
> >     L = [ {{<<"longitude">>,6.1457}, {<<"latitude">>,46.2022}},
> >           {{<<"longitude">>,2.3387}, {<<"latitude">>,48.8582}},
> >           ... ]
> >
> >     and a specific coordinate X = {{<<"longitude">>,-73.5848},
> >     {<<"latitude">>,45.4995}}.
> >
> >     Question: how can i find the nearest coordinates to X from L (sorted
> >     from the nearest to the farest)?
> >
> >     /Frank
> >
>