7

geoJSON ファイルを使用して国を描​​画するマップがあります。次に、各国を中心に円を描きたいと思います。しかし、複数の境界地域を持つ国 (米国には本土、ハワイ、アラスカがあります) では、最大の境界地域に円が必要です。さまざまな境界領域の面積を比較してこれを実行しようとしていますが、理解できない理由で機能していません。

これは geoJSON の例で、オーストラリアに複数の境界領域があることを示しています。

{"type":"Feature","properties":{"name":"Australia"},"geometry":{"type":"MultiPolygon","coordinates":[[[[145.397978,-40.792549],[146.364121,-41.137695],[146.908584,-41.000546],[147.689259,-40.808258],[148.289068,-40.875438],[148.359865,-42.062445],[148.017301,-42.407024],[147.914052,-43.211522],[147.564564,-42.937689],[146.870343,-43.634597],[146.663327,-43.580854],[146.048378,-43.549745],[145.43193,-42.693776],[145.29509,-42.03361],[144.718071,-41.162552],[144.743755,-40.703975],[145.397978,-40.792549]]],[[[143.561811,-13.763656],[143.922099,-14.548311],[144.563714,-14.171176],[144.894908,-14.594458],[145.374724,-14.984976],[145.271991,-15.428205],[145.48526,-16.285672],[145.637033,-16.784918],[145.888904,-16.906926],[146.160309,-17.761655],[146.063674,-18.280073],[146.387478,-18.958274],[147.471082,-19.480723],[148.177602,-19.955939],[148.848414,-20.39121],[148.717465,-20.633469],[149.28942,-21.260511],[149.678337,-22.342512],[150.077382,-22.122784],[150.482939,-22.556142],[150.727265,-22.402405],[150.899554,-23.462237],[151.609175,-24.076256],[152.07354,-24.457887],[152.855197,-25.267501],[153.136162,-26.071173],[153.161949,-26.641319],[153.092909,-27.2603],[153.569469,-28.110067],[153.512108,-28.995077],[153.339095,-29.458202],[153.069241,-30.35024],[153.089602,-30.923642],[152.891578,-31.640446],[152.450002,-32.550003],[151.709117,-33.041342],[151.343972,-33.816023],[151.010555,-34.31036],[150.714139,-35.17346],[150.32822,-35.671879],[150.075212,-36.420206],[149.946124,-37.109052],[149.997284,-37.425261],[149.423882,-37.772681],[148.304622,-37.809061],[147.381733,-38.219217],[146.922123,-38.606532],[146.317922,-39.035757],[145.489652,-38.593768],[144.876976,-38.417448],[145.032212,-37.896188],[144.485682,-38.085324],[143.609974,-38.809465],[142.745427,-38.538268],[142.17833,-38.380034],[141.606582,-38.308514],[140.638579,-38.019333],[139.992158,-37.402936],[139.806588,-36.643603],[139.574148,-36.138362],[139.082808,-35.732754],[138.120748,-35.612296],[138.449462,-35.127261],[138.207564,-34.384723],[137.71917,-35.076825],[136.829406,-35.260535],[137.352371,-34.707339],[137.503886,-34.130268],[137.890116,-33.640479],[137.810328,-32.900007],[136.996837,-33.752771],[136.372069,-34.094766],[135.989043,-34.890118],[135.208213,-34.47867],[135.239218,-33.947953],[134.613417,-33.222778],[134.085904,-32.848072],[134.273903,-32.617234],[132.990777,-32.011224],[132.288081,-31.982647],[131.326331,-31.495803],[129.535794,-31.590423],[128.240938,-31.948489],[127.102867,-32.282267],[126.148714,-32.215966],[125.088623,-32.728751],[124.221648,-32.959487],[124.028947,-33.483847],[123.659667,-33.890179],[122.811036,-33.914467],[122.183064,-34.003402],[121.299191,-33.821036],[120.580268,-33.930177],[119.893695,-33.976065],[119.298899,-34.509366],[119.007341,-34.464149],[118.505718,-34.746819],[118.024972,-35.064733],[117.295507,-35.025459],[116.625109,-35.025097],[115.564347,-34.386428],[115.026809,-34.196517],[115.048616,-33.623425],[115.545123,-33.487258],[115.714674,-33.259572],[115.679379,-32.900369],[115.801645,-32.205062],[115.689611,-31.612437],[115.160909,-30.601594],[114.997043,-30.030725],[115.040038,-29.461095],[114.641974,-28.810231],[114.616498,-28.516399],[114.173579,-28.118077],[114.048884,-27.334765],[113.477498,-26.543134],[113.338953,-26.116545],[113.778358,-26.549025],[113.440962,-25.621278],[113.936901,-25.911235],[114.232852,-26.298446],[114.216161,-25.786281],[113.721255,-24.998939],[113.625344,-24.683971],[113.393523,-24.384764],[113.502044,-23.80635],[113.706993,-23.560215],[113.843418,-23.059987],[113.736552,-22.475475],[114.149756,-21.755881],[114.225307,-22.517488],[114.647762,-21.82952],[115.460167,-21.495173],[115.947373,-21.068688],[116.711615,-20.701682],[117.166316,-20.623599],[117.441545,-20.746899],[118.229559,-20.374208],[118.836085,-20.263311],[118.987807,-20.044203],[119.252494,-19.952942],[119.805225,-19.976506],[120.85622,-19.683708],[121.399856,-19.239756],[121.655138,-18.705318],[122.241665,-18.197649],[122.286624,-17.798603],[122.312772,-17.254967],[123.012574,-16.4052],[123.433789,-17.268558],[123.859345,-17.069035],[123.503242,-16.596506],[123.817073,-16.111316],[124.258287,-16.327944],[124.379726,-15.56706],[124.926153,-15.0751],[125.167275,-14.680396],[125.670087,-14.51007],[125.685796,-14.230656],[126.125149,-14.347341],[126.142823,-14.095987],[126.582589,-13.952791],[127.065867,-13.817968],[127.804633,-14.276906],[128.35969,-14.86917],[128.985543,-14.875991],[129.621473,-14.969784],[129.4096,-14.42067],[129.888641,-13.618703],[130.339466,-13.357376],[130.183506,-13.10752],[130.617795,-12.536392],[131.223495,-12.183649],[131.735091,-12.302453],[132.575298,-12.114041],[132.557212,-11.603012],[131.824698,-11.273782],[132.357224,-11.128519],[133.019561,-11.376411],[133.550846,-11.786515],[134.393068,-12.042365],[134.678632,-11.941183],[135.298491,-12.248606],[135.882693,-11.962267],[136.258381,-12.049342],[136.492475,-11.857209],[136.95162,-12.351959],[136.685125,-12.887223],[136.305407,-13.29123],[135.961758,-13.324509],[136.077617,-13.724278],[135.783836,-14.223989],[135.428664,-14.715432],[135.500184,-14.997741],[136.295175,-15.550265],[137.06536,-15.870762],[137.580471,-16.215082],[138.303217,-16.807604],[138.585164,-16.806622],[139.108543,-17.062679],[139.260575,-17.371601],[140.215245,-17.710805],[140.875463,-17.369069],[141.07111,-16.832047],[141.274095,-16.38887],[141.398222,-15.840532],[141.702183,-15.044921],[141.56338,-14.561333],[141.63552,-14.270395],[141.519869,-13.698078],[141.65092,-12.944688],[141.842691,-12.741548],[141.68699,-12.407614],[141.928629,-11.877466],[142.118488,-11.328042],[142.143706,-11.042737],[142.51526,-10.668186],[142.79731,-11.157355],[142.866763,-11.784707],[143.115947,-11.90563],[143.158632,-12.325656],[143.522124,-12.834358],[143.597158,-13.400422],[143.561811,-13.763656]]]]},"id":"AUS"},

そして、ここに異なる境界領域の領域を比較しようとするコードがあります。そのifステートメントでは、国に複数の境界地域があるかどうかを調べようとしています (それは機能しているようです)。次に、forブロック内で最大のものを選択します。

問題: 私が取得している「面積」の値はすべて 0 であり、coords常に最大ではなく、最初の境界領域から選択されています。

function calculateCountryCenter(country) {

    var coords;

    //Check if the country has more than one bounding region.
    if (country.geometry.coordinates.length > 1) {

        coords = country.geometry.coordinates[0][0];

        var regionArea = path.area(country.geometry.coordinates[0]);

        for (var i=0; i<country.geometry.coordinates.length; i++) {
            if (path.area(country.geometry.coordinates[i]) > regionArea) {

                coords = country.geometry.coordinates[i][0];
            }
        }     

    } else {    
        coords = country.geometry.coordinates[0];
    }

    var averageCoords = [0,0];
    coords.forEach(function(coord) {
        averageCoords[0] += coord[0]
        averageCoords[1] += coord[1]
    });

    averageCoords[0] = averageCoords[0] / coords.length
    averageCoords[1] = averageCoords[1] / coords.length
    return averageCoords;

}

これがパスの定義です。

      var path = d3.geo.path().projection(projection)

どんなガイダンスでも大歓迎です。どうもありがとう。

4

3 に答える 3

9

Shoelace アルゴリズムを使用して、任意の多角形の面積を計算できます。

function polygonArea(points) {
  var sum = 0.0;
  var length = points.length;
  if (length < 3) {
    return sum;
  }
  points.forEach(function(d1, i1) {
    i2 = (i1 + 1) % length;
    d2 = points[i2];
    sum += (d2[1] * d1[0]) - (d1[1] * d2[0]);
  });
  return sum / 2;
}

polygonArea([[0,0], [4,0], [4,3]]);  // 6

反時計回りのポリゴンには正の領域があり、時計回りのポリゴンには負の領域があることに注意してください。通常、自己交差ポリゴンには時計回りと反時計回りの両方の領域があるため、それらの領域は相殺されます。

于 2013-07-30T16:12:36.157 に答える
4

まだ誰も完全に実装された回答を追加していないという理由だけで、私は自分の質問に答えることにしました. 元の質問で指定されているように、geoJSON を取得し、複数の境界地域を持つ国の最大の境界地域の座標を返すコードを次に示します。境界地域が 1 つしかない国の場合、1 つの境界地域の座標を返します。(ここではスタンドアロン メソッドにするためにコードを少し変更する必要がありましたが、エラーがないことは確かです。)

function getLargestBoundingRegion(country) {

var largestRegionCoords;
var path = d3.geo.path()

//Check if the country has more than one bounding region.
if (country.geometry.coordinates.length > 1) {

    var regionToReturn = {        
        "type": "Feature",
        "geometry": {
            "type": "Polygon", 
            "coordinates": country.geometry.coordinates[0]},            
        };

    for (var i=1; i<country.geometry.coordinates.length; i++) {

        var testRegion = {        
                    "type": "Feature",
                "geometry": {
                    "type": "Polygon", 
                    "coordinates": country.geometry.coordinates[i]},            
            };

        if (path.area(testRegion) > path.area(regionToReturn)) {
            regionToReturn = testRegion;    
            largestRegionCoords = country.geometry.coordinates[i][0];    
            }
        }

    } else {    
        largestRegionCoords = country.geometry.coordinates[0];
    }

return largestRegionCoords;
于 2013-04-16T15:14:30.880 に答える