转换为 OSGB36(红宝石)

Question

我使用以下代码尝试将OSGB36转换为WGS84，

#!/usr/bin/ruby
# Some UK Ordnance Survey coordinate conversions in pure ruby.
#
# WGS84 lat/lons -> OSGB64 lat/lons-> OS Eastings & Northings 

# http://www.movable-type.co.uk/scripts/latlong-convert-coords.html
# (c) Chris Veness 2005-2010  Released under an LGPL license
# http://www.fsf.org/licensing/licenses/lgpl.html
# Ported to ruby by Harry Wood

#ellipse parameters
@e = { :wgs84 =>   { :a=> 6378137,     :b=> 6356752.3142, :f=> 1 / 298.257223563 },
      :airy1830 => { :a=> 6377563.396, :b=> 6356256.910,  :f=> 1 / 299.3249646   } };
#helmert transform parameters
@h = { :wgs84toOSGB36 => { :tx=> -446.448,  :ty=>  125.157,  :tz=> -542.060,  # m
                           :rx=>  -0.1502,  :ry=>   -0.2470, :rz=>  -0.8421,  # sec
                           :s=>   20.4894 },                                  # ppm
       :osgb36toWGS84 => { :tx=>  446.448,  :ty=> -125.157,  :tz=>  542.060,
                           :rx=>    0.1502, :ry=>    0.2470, :rz=>    0.8421,
                           :s=>   -20.4894 } };

def convertOSGB36toWGS84(p1lat, p1lon, p1height) 
   p2 = convert(p1lat, p1lon, p1height, @e[:airy1830], @h[:osgb36toWGS84], @e[:wgs84]);
   return p2;
end

def convertWGS84toOSGB36(p1lat, p1lon, p1height)
   p2 = convert(p1lat, p1lon, p1height, @e[:wgs84], @h[:wgs84toOSGB36], @e[:airy1830]);
   return p2;
end
def convert(p1lat, p1lon, p1height, e1, t, e2)
   # -- convert polar to cartesian coordinates (using ellipse 1)
   p1lat = toRad(p1lat); p1lon = toRad(p1lon); 
   a = e1[:a]; b = e1[:b];
   sinPhi = Math.sin(p1lat); cosPhi = Math.cos(p1lat);
   sinLambda = Math.sin(p1lon); cosLambda = Math.cos(p1lon);
   h = p1height;
   eSq = (a*a - b*b) / (a*a);
   nu = a / Math.sqrt(1 - eSq*sinPhi*sinPhi);
   x1 = (nu+h) * cosPhi * cosLambda;
   y1 = (nu+h) * cosPhi * sinLambda;
   z1 = ((1-eSq)*nu + h) * sinPhi;

   # -- apply helmert transform using appropriate params
   tx = t[:tx]; ty = t[:ty]; tz = t[:tz];
   rx = t[:rx] / 3600 * Math::PI/180;  #normalise seconds to radians
   ry = t[:ry] / 3600 * Math::PI/180;
   rz = t[:rz] / 3600 * Math::PI/180;
   s1 = t[:s] / 1e6 + 1;              #normalise ppm to (s+1)
   #apply transform
   x2 = tx + x1*s1 - y1*rz + z1*ry;
   y2 = ty + x1*rz + y1*s1 - z1*rx;
   z2 = tz - x1*ry + y1*rx + z1*s1;

   # -- convert cartesian to polar coordinates (using ellipse 2)
   a = e2[:a]; b = e2[:b];
   precision = 4 / a;  # results accurate to around 4 metres
   eSq = (a*a - b*b) / (a*a);
   p = Math.sqrt(x2*x2 + y2*y2);
   phi = Math.atan2(z2, p*(1-eSq)); phiP = 2 * Math::PI;
   while ( (phi-phiP).abs > precision) do
      nu = a / Math.sqrt(1 - eSq*Math.sin(phi)*Math.sin(phi));
      phiP = phi;
      phi = Math.atan2(z2 + eSq*nu*Math.sin(phi), p);
   end
   lambda = Math.atan2(y2, x2);
   h = p/Math.cos(phi) - nu;
   #return array [lat,lon,height]
   return [ toDeg(phi), toDeg(lambda), h ]; 
end


# http://www.movable-type.co.uk/scripts/latlong-gridref.html
# (c) Chris Veness 2005-2010  Released under an LGPL license
# http://www.fsf.org/licensing/licenses/lgpl.html
# Ported to ruby by Harry Wood
# OSGB36 lat lon to OS UK grid eastings & northings
def LatLongToOSGrid(lat, long)
   lat = toRad(lat);
   lon = toRad(long);
   a = 6377563.396; b = 6356256.910          # Airy 1830 major & minor semi-axes
   f0 = 0.9996012717                         # NatGrid scale factor on central meridian
   lat0 = toRad(49); lon0 = toRad(-2)        # NatGrid true origin
   n0 = -100000; e0 = 400000;                # northing & easting of true origin, metres
   e2 = 1 - (b*b) / (a*a);                   # eccentricity squared
   n = (a-b) / (a+b); n2 = n*n; n3 = n*n*n;
   cosLat = Math.cos(lat); sinLat = Math.sin(lat);
   nu = a*f0/Math.sqrt(1-e2*sinLat*sinLat);              # transverse radius of curvature
   rho = a*f0*(1-e2) / ( (1-e2*sinLat*sinLat) ** 1.5);  # meridional radius of curvature
   eta2 = nu/rho-1;
   ma = (1 + n + (5/4)*n2 + (5/4)*n3) * (lat-lat0);
   mb = (3*n + 3*n*n + (21/8)*n3) * Math.sin(lat-lat0) * Math.cos(lat+lat0);
   mc = ((15/8)*n2 + (15/8)*n3) * Math.sin(2*(lat-lat0)) * Math.cos(2*(lat+lat0));
   md = (35/24)*n3 * Math.sin(3*(lat-lat0)) * Math.cos(3*(lat+lat0));
   m = b * f0 * (ma - mb + mc - md);              # meridional arc
   cos3lat = cosLat*cosLat*cosLat;
   cos5lat = cos3lat*cosLat*cosLat;
   tan2lat = Math.tan(lat)*Math.tan(lat);
   tan4lat = tan2lat*tan2lat;
   i = m + n0;
   ii = (nu/2)*sinLat*cosLat;
   iii = (nu/24)*sinLat*cos3lat*(5-tan2lat+9*eta2);
   iiiA = (nu/720)*sinLat*cos5lat*(61-58*tan2lat+tan4lat);
   iv = nu*cosLat;
   v = (nu/6)*cos3lat*(nu/rho-tan2lat);
   vi = (nu/120) * cos5lat * (5 - 18*tan2lat + tan4lat + 14*eta2 - 58*tan2lat*eta2);
   dLon = lon-lon0;
   dLon2 = dLon*dLon
   dLon3 = dLon2*dLon
   dLon4 = dLon3*dLon
   dLon5 = dLon4*dLon
   dLon6 = dLon5*dLon
   n = i + ii*dLon2 + iii*dLon4 + iiiA*dLon6;
   e = e0 + iv*dLon + v*dLon3 + vi*dLon5;
   return [ e, n ]   #return raw easting and northings instead
   #return gridrefNumToLet( e, n, 8) 
end
def toRad(degrees)
   return degrees * Math::PI / 180;
end
def toDeg(rads)
   return rads * 180 / Math::PI 
end
#convert numeric grid reference (in metres) to standard-form grid ref
def gridrefNumToLet(e, n, digits) 
   #get the 100km-grid indices
   e100k = (e / 100000).floor; n100k = (n / 100000).floor;
   return '' if (e100k<0 or e100k>6 or n100k<0 or n100k>12)
   #translate those into numeric equivalents of the grid letters
   l1 = (19-n100k) - (19-n100k) % 5 + ((e100k+10) / 5).floor;
   l2 = (19-n100k) * 5 % 25 + e100k % 5;
   # compensate for skipped 'I' and build grid letter-pairs         
   l1=l1+1 if (l1 > 7)
   l2=l2+1 if (l2 > 7) 
   letPair =  (l1 +'A'[0]).chr +  (l2 +'A'[0]).chr ;
   # strip 100km-grid indices from easting & northing, and reduce precision
   e = ( (e % 100000) / (10 ** (5 - digits / 2)) ).floor;
   n = ( (n % 100000) / (10 ** (5 - digits / 2)) ).floor;
   gridRef = letPair + e.to_s.rjust(digits / 2) + n.to_s.rjust(digits / 2)
   return gridRef;
end

# Example WGS84 lat/lon to convert
lon = -0.10322
lat = 51.52237
height = 0
osgb36point = convertWGS84toOSGB36(lat,lon, height)
oslat = osgb36point[0]
oslon = osgb36point[1]
osh = osgb36point[2]
osUKgridPoint = LatLongToOSGrid(oslat,oslon)
easting  = osUKgridPoint[0].round
northing = osUKgridPoint[1].round
gridrefLetters = gridrefNumToLet(easting,northing, 8)
puts "wgs84 lat:" + lat.to_s + ", wgs84 lon:" + lon.to_s
puts "http://www.openstreetmap.org/?mlat=" + lat.to_s + "&mlon=" + lon.to_s + "&zoom=16"
puts "Converts to:";
puts "osgb36 lat:" + oslat.to_s + ", osgb36 lon:" + oslon.to_s
puts "Converts to:";
puts "easting:" + easting.to_s + ", northing:" + northing.to_s + "  As a grid ref:" + gridrefLetters
puts "http://streetmap.co.uk/grid/" + easting.to_s + "_" + northing.to_s + "_106"

我似乎无法让它工作，有人可以给我一个使用 OSGB36toWGS84 方法的示例方法。它确实运行（在我编辑的那个上），但是输出不正确。

我的代码：

lon =  521490
lat =  192263
height = 0
osgb36point = convertOSGB36toWGS84(lat,lon, height)
oslat = osgb36point[0]
oslon = osgb36point[1]
osh = osgb36point[2]
osUKgridPoint = LatLongToOSGrid(oslat,oslon)
easting  = osUKgridPoint[0].round
northing = osUKgridPoint[1].round

输出：

wgs84 lat:192263, wgs84 lon:521490
Converts to:
osgb36 lat:23.00619802206627, osgb36 lon:-149.99650128215052
Converts to:
easting:-33856949, northing:56599846

下面是博客条目（请参阅纯 Ruby 实现部分）http://www.harrywood.co.uk/blog/category/maps/page/2/

有什么想法吗？

Answer 1

从博客文章中看，您正在使用不会改变的地理数据（管线的位置），因此提前进行一次转换似乎更有意义，而不是即时转换。 这意味着您可以使用 ogr2ogr 并完全避免编写转换例程： http://www.mercatorgeosystems.com/blog-articles/2008/05/30/using-ogr2ogr-to-re-project-a-shape-file/