euler_map_projection_piy.js

// Euler Spiral map projection
// For https://tmcw.github.io/projectityourself/

let lon_look = [
    [-180, -89.33633981999999],
    [-177, -80.661710898],
    [-174, -73.825305678],
    [-171, -70.20639653399999],
    [-167.99999999999997, -70.475119848],
    [-165, -74.51836227],
    [-162.00000000000003, -81.525147768],
    [-159, -90.192768336],
    [-156, -98.99807815800001],
    [-152.99999999999997, -106.47557963999999],
    [-150, -111.452716044],
    [-147.00000000000003, -113.208958206],
    [-144, -111.54419368199999],
    [-141, -106.759551636],
    [-137.99999999999997, -99.56729546999999],
    [-135, -90.954400824],
    [-132.00000000000003, -82.026830178],
    [-129, -73.859223384],
    [-126, -67.369204692],
    [-122.99999999999999, -63.22838022],
    [-120, -61.814822111999995],
    [-117, -63.205511867999995],
    [-114, -67.202517204],
    [-111, -73.38385639799999],
    [-108, -81.168978474],
    [-105, -89.889241428],
    [-102, -98.85526925399999],
    [-99, -107.41515921],
    [-96, -114.99978303],
    [-93, -121.153563018],
    [-90, -125.550892818],
    [-87, -127.999702332],
    [-83.99999999999999, -128.434513914],
    [-81.00000000000001, -126.901737774],
    [-78, -123.53999138999998],
    [-75, -118.557992088],
    [-72, -112.21216533],
    [-68.99999999999999, -104.785618572],
    [-66.00000000000001, -96.569623998],
    [-63, -87.848283276],
    [-60, -78.886646532],
    [-57, -69.922241568],
    [-54, -61.159741992],
    [-51, -52.76835702],
    [-48, -44.881450758],
    [-45, -37.597880016],
    [-41.99999999999999, -30.984562422000003],
    [-39, -25.07983587],
    [-36, -19.897237332],
    [-33.00000000000001, -15.4293997194],
    [-30, -11.6518379148],
    [-27, -8.5264599978],
    [-24, -6.0046978788],
    [-20.999999999999996, -4.0301990514],
    [-18, -2.5410596418],
    [-15, -1.4716080424800002],
    [-12, -0.7537696491600001],
    [-9, -0.31805787672],
    [-6, -0.09424611856800001],
    [-3, -0.0117809594748],
    [0, 0],
    [3, 0.0117809594748],
    [6, 0.09424611856800001],
    [9, 0.31805787672],
    [12, 0.7537696491600001],
    [15, 1.4716080424800002],
    [18, 2.5410596418],
    [20.999999999999996, 4.0301990514],
    [24, 6.0046978788],
    [27, 8.5264599978],
    [30, 11.6518379148],
    [33.00000000000001, 15.4293997194],
    [36, 19.897237332],
    [39, 25.07983587],
    [41.99999999999999, 30.984562422000003],
    [45, 37.597880016],
    [48, 44.881450758],
    [51, 52.76835702],
    [54, 61.159741992],
    [57, 69.922241568],
    [60, 78.886646532],
    [63, 87.848283276],
    [66.00000000000001, 96.569623998],
    [68.99999999999999, 104.785618572],
    [72, 112.21216533],
    [75, 118.557992088],
    [78, 123.53999138999998],
    [81.00000000000001, 126.901737774],
    [83.99999999999999, 128.434513914],
    [87, 127.999702332],
    [90, 125.550892818],
    [93, 121.153563018],
    [96, 114.99978303],
    [99, 107.41515921],
    [102, 98.85526925399999],
    [105, 89.889241428],
    [108, 81.168978474],
    [111, 73.38385639799999],
    [114, 67.202517204],
    [117, 63.205511867999995],
    [120, 61.814822111999995],
    [122.99999999999999, 63.22838022],
    [126, 67.369204692],
    [129, 73.859223384],
    [132.00000000000003, 82.026830178],
    [135, 90.954400824],
    [137.99999999999997, 99.56729546999999],
    [141, 106.759551636],
    [144, 111.54419368199999],
    [147.00000000000003, 113.208958206],
    [150, 111.452716044],
    [152.99999999999997, 106.47557963999999],
    [156, 98.99807815800001],
    [159, 90.192768336],
    [162.00000000000003, 81.525147768],
    [165, 74.51836227],
    [167.99999999999997, 70.475119848],
    [171, 70.20639653399999],
    [174, 73.825305678],
    [177, 80.661710898],
    [180, 89.33633981999999],
];

let lat_look = [
    [-90, -54.514871037],
    [-88.5, -53.479565874],
    [-87, -50.613880518],
    [-85.5, -46.535394951],
    [-83.99999999999999, -42.074248653],
    [-82.5, -38.093741666999996],
    [-81.00000000000001, -35.324457291],
    [-79.5, -34.241917176],
    [-78, -35.004374658],
    [-76.49999999999999, -37.45328472],
    [-75, -41.167170864],
    [-73.50000000000001, -45.55181772899999],
    [-72, -49.946526522],
    [-70.5, -53.727138161999996],
    [-68.99999999999999, -56.390553882000006],
    [-67.5, -57.611178890999994],
    [-66.00000000000001, -57.265744041],
    [-64.5, -55.428261534],
    [-63, -52.34077215000001],
    [-61.49999999999999, -48.367769499],
    [-60, -43.942806549000004],
    [-58.5, -39.515098104],
    [-57, -35.502348141],
    [-55.5, -32.253994575],
    [-54, -30.026963448],
    [-52.5, -28.974154158],
    [-51, -29.14441884],
    [-49.5, -30.491831016000003],
    [-48, -32.891551506],
    [-46.5, -36.159527943],
    [-45, -40.073505839999996],
    [-43.5, -44.393275035],
    [-41.99999999999999, -48.878620515],
    [-40.50000000000001, -53.304007419],
    [-39, -57.469540923000004],
    [-37.5, -61.208166699],
    [-36, -64.389395061],
    [-34.49999999999999, -66.920042943],
    [-33.00000000000001, -68.74259994],
    [-31.5, -69.831856935],
    [-30, -70.190406036],
    [-28.5, -69.843550815],
    [-27, -68.834071908],
    [-25.5, -67.217190876],
    [-24, -65.05597547100001],
    [-22.5, -62.417339172],
    [-20.999999999999996, -59.36871167100001],
    [-19.5, -55.975396851],
    [-18, -52.29859023],
    [-16.500000000000004, -48.39399774899999],
    [-15, -44.310980330999996],
    [-13.5, -40.092140583],
    [-12, -35.773268328],
    [-10.499999999999998, -31.383566478],
    [-9, -26.946087848999998],
    [-7.5, -22.478323535999998],
    [-6, -17.992895184],
    [-4.5, -13.498313787],
    [-3, -8.9997779367],
    [-1.5, -4.4999930600999996],
    [0, 0],
    [1.5, 4.4999930600999996],
    [3, 8.9997779367],
    [4.5, 13.498313787],
    [6, 17.992895184],
    [7.5, 22.478323535999998],
    [9, 26.946087848999998],
    [10.499999999999998, 31.383566478],
    [12, 35.773268328],
    [13.5, 40.092140583],
    [15, 44.310980330999996],
    [16.500000000000004, 48.39399774899999],
    [18, 52.29859023],
    [19.5, 55.975396851],
    [20.999999999999996, 59.36871167100001],
    [22.5, 62.417339172],
    [24, 65.05597547100001],
    [25.5, 67.217190876],
    [27, 68.834071908],
    [28.5, 69.843550815],
    [30, 70.190406036],
    [31.5, 69.831856935],
    [33.00000000000001, 68.74259994],
    [34.49999999999999, 66.920042943],
    [36, 64.389395061],
    [37.5, 61.208166699],
    [39, 57.469540923000004],
    [40.50000000000001, 53.304007419],
    [41.99999999999999, 48.878620515],
    [43.5, 44.393275035],
    [45, 40.073505839999996],
    [46.5, 36.159527943],
    [48, 32.891551506],
    [49.5, 30.491831016000003],
    [51, 29.14441884],
    [52.5, 28.974154158],
    [54, 30.026963448],
    [55.5, 32.253994575],
    [57, 35.502348141],
    [58.5, 39.515098104],
    [60, 43.942806549000004],
    [61.49999999999999, 48.367769499],
    [63, 52.34077215000001],
    [64.5, 55.428261534],
    [66.00000000000001, 57.265744041],
    [67.5, 57.611178890999994],
    [68.99999999999999, 56.390553882000006],
    [70.5, 53.727138161999996],
    [72, 49.946526522],
    [73.50000000000001, 45.55181772899999],
    [75, 41.167170864],
    [76.49999999999999, 37.45328472],
    [78, 35.004374658],
    [79.5, 34.241917176],
    [81.00000000000001, 35.324457291],
    [82.5, 38.093741666999996],
    [83.99999999999999, 42.074248653],
    [85.5, 46.535394951],
    [87, 50.613880518],
    [88.5, 53.479565874],
    [90, 54.514871037],
];

function project(x, y) {
    let xx = 0;
    let yy = 0;

    for (let i = 0; i < lon_look.length; i++) {
        if (i == lon_look.length-1) {
            xx = lon_look[i][1];
            break;
        }

        if (lon_look[i][0] <= x && lat_look[i+1][0] >= x) {
            xx = (lon_look[i][1] + lon_look[i+1][1]) / 2.0;
            break;
        }
    }

    for (let i = 0; i < lat_look.length; i++) {
        if (i == lat_look.length-1) {
            yy = lat_look[i][1];
            break;
        }

        if (lat_look[i][0] <= x && lat_look[i+1][0] >= x) {
            yy = (lat_look[i][1] + lat_look[i+1][1]) / 2.0;
            break;
        }
    }
    
    return [xx, yy];
}