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POConvert planar x/y to lat/long
 

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  1. POConvert planar x/y to lat/long
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    <p>Im trying to write a program that takes new york city x/y coords and turns them into lat/lng decimal points. Im new to planar/globe mapping. Ive included the constants that NYC has provided on their website. Also if there is a good article on how to do this I would love to learn! Below is the program I have written along with commented output at the bottom and also what the ideal values should be. Im kinda just stumbling in the dark on this.</p> <pre><code>#!/usr/bin/python from math import * """ Supplied by NYC Lambert Conformal Conic: Standard Parallel: 40.666667 Standard Parallel: 41.033333 Longitude of Central Meridian: -74.000000 Latitude of Projection Origin: 40.166667 False Easting: 984250.000000 False Northing: 0.000000 """ x = 981106 #nyc x coord y = 195544 #nyc y coord a = 6378137 #' major radius of ellipsoid, map units (NAD 83) e = 0.08181922146 #' eccentricity of ellipsoid (NAD 83) angRad = pi/180 #' number of radians in a degree pi4 = pi/4 #' Pi / 4 p0 = 40.166667 * angRad #' latitude of origin p1 = 40.666667 * angRad #' latitude of first standard parallel p2 = 41.033333 * angRad #' latitude of second standard parallel m0 = -74.000000 * angRad #' central meridian x0 = 984250.000000 #' False easting of central meridian, map units m1 = cos(p1) / sqrt(1 - ((e ** 2) * sin(p1) ** 2)) m2 = cos(p2) / sqrt(1 - ((e ** 2) * sin(p2) ** 2)) t0 = tan(pi4 - (p0 / 2)) t1 = tan(pi4 - (p1 / 2)) t2 = tan(pi4 - (p2 / 2)) t0 = t0 / (((1 - (e * (sin(p0)))) / (1 + (e * (sin(p0)))))**(e / 2)) t1 = t1 / (((1 - (e * (sin(p1)))) / (1 + (e * (sin(p1)))))**(e / 2)) t2 = t2 / (((1 - (e * (sin(p2)))) / (1 + (e * (sin(p2)))))**(e / 2)) n = log(m1 / m2) / log(t1 / t2) f = m1 / (n * (t1 ** n)) rho0 = a * f * (t0 ** n) x = x - x0 pi2 = pi4 * 2 rho = sqrt((x ** 2) + ((rho0 - y) ** 2)) theta = atan(x / (rho0 - y)) t = (rho / (a * f)) ** (1 / n) lon = (theta / n) + m0 x = x + x0 lat0 = pi2 - (2 * atan(t)) part1 = (1 - (e * sin(lat0))) / (1 + (e * sin(lat0))) lat1 = pi2 - (2 * atan(t * (part1 ** (e / 2)))) while abs(lat1 - lat0) &lt; 0.000000002: lat0 = lat1 part1 = (1 - (e * sin(lat0))) / (1 + (e * sin(lat0))) lat1 = pi2 - (2 * atan(t * (part1 ^ (e / 2)))) lat = lat1 / angRad lon = lon / angRad print lat,lon #output : 41.9266666432 -74.0378981653 #should be 40.703778, -74.011829 </code></pre> <p>Im pretty stuck, I have a ton of these that need geo-coded Thanks for any help! </p>
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    1. COMaybe http://en.wikipedia.org/wiki/Map_projection could get you started?
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      1. USJouni K. Seppänen
    2. COMore details about the projection used: http://en.wikipedia.org/wiki/Lambert_conformal_conic_projection
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    3. COJust read that article and started implementing the formula then I realized that I am doing an ellipsoidal transformation and that formula isn't there all it says is: Formulæ for ellipsoidal datums are more involved.
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