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HTML 

              
                <h1>
  D3 Map Projections
</h1>

<p>
  geoOrthographic vs.
  <select id="projectionChoice">
    <option value="geoAiry">geoAiry</option>
    <option value="geoAirocean">geoAirocean</option>
    <option value="geoAitoff">geoAitoff</option>
    <option value="geoAlbers">geoAlbers</option>
    <option value="geoArmadillo">geoArmadillo</option>
    <option value="geoAugust">geoAugust</option>
    <option value="geoAzimuthalEqualArea">geoAzimuthalEqualArea</option>
    <option value="geoAzimuthalEquidistant">geoAzimuthalEquidistant</option>
    <option value="geoBaker">geoBaker</option>
    <option value="geoBerghaus">geoBerghaus</option>
    <option value="geoBertin1953">geoBertin1953</option>
    <option value="geoBoggs">geoBoggs</option>
    <option value="geoBonne">geoBonne</option>
    <option value="geoBottomley">geoBottomley</option>
    <option value="geoBromley">geoBromley</option>
    <option value="geoCahillKeyes">geoCahillKeyes</option>
    <option value="geoCollignon">geoCollignon</option>
    <option value="geoComplexLog">geoComplexLog</option>
    <option value="geoConicEqualArea">geoConicEqualArea</option>
    <option value="geoConicEquidistant">geoConicEquidistant</option>
    <option value="geoCox">geoCox</option>
    <option value="geoCraig">geoCraig</option>
    <option value="geoCraster">geoCraster</option>
    <option value="geoCubic">geoCubic</option>
    <option value="geoCylindricalEqualArea">geoCylindricalEqualArea</option>
    <option value="geoCylindricalStereographic">geoCylindricalStereographic</option>
    <option value="geoDodecahedral">geoDodecahedral</option>
    <option value="geoEckert1">geoEckert1</option>
    <option value="geoEckert2">geoEckert2</option>
    <option value="geoEckert3">geoEckert3</option>
    <option value="geoEckert4">geoEckert4</option>
    <option value="geoEckert5">geoEckert5</option>
    <option value="geoEckert6">geoEckert6</option>
    <option value="geoEisenlohr">geoEisenlohr</option>
    <option value="geoEqualEarth">geoEqualEarth</option>
    <option value="geoEquirectangular">geoEquirectangular</option>
    <option value="geoFahey">geoFahey</option>
    <option value="geoFoucaut">geoFoucaut</option>
    <option value="geoFoucautSinusoidal">geoFoucautSinusoidal</option>
    <option value="geoGilbert">geoGilbert</option>
    <option value="geoGingery">geoGingery</option>
    <option value="geoGinzburg4">geoGinzburg4</option>
    <option value="geoGinzburg5">geoGinzburg5</option>
    <option value="geoGinzburg6">geoGinzburg6</option>
    <option value="geoGinzburg8">geoGinzburg8</option>
    <option value="geoGinzburg9">geoGinzburg9</option>
    <option value="geoGnomonic">geoGnomonic</option>
    <option value="geoGringorten">geoGringorten</option>
    <option value="geoGringortenQuincuncial">geoGringortenQuincuncial</option>
    <option value="geoGuyou">geoGuyou</option>
    <option value="geoHammer">geoHammer</option>
    <option value="geoHammerRetroazimuthal">geoHammerRetroazimuthal</option>
    <option value="geoHealpix">geoHealpix</option>
    <option value="geoHill">geoHill</option>
    <option value="geoHomolosine">geoHomolosine</option>
    <option value="geoHufnagel">geoHufnagel</option>
    <option value="geoHyperelliptical">geoHyperelliptical</option>
    <option value="geoIcosahedral">geoIcosahedral</option>
    <option value="geoImago">geoImago</option>
    <option value="geoInterruptedBoggs">geoInterruptedBoggs</option>
    <option value="geoInterruptedHomolosine">geoInterruptedHomolosine</option>
    <option value="geoInterruptedMollweide">geoInterruptedMollweide</option>
    <option value="geoInterruptedMollweideHemispheres">geoInterruptedMollweideHemispheres</option>
    <option value="geoInterruptedQuarticAuthalic">geoInterruptedQuarticAuthalic</option>
    <option value="geoInterruptedSinuMollweide">geoInterruptedSinuMollweide</option>
    <option value="geoInterruptedSinusoidal">geoInterruptedSinusoidal</option>
    <option value="geoKavrayskiy7">geoKavrayskiy7</option>
    <option value="geoLagrange">geoLagrange</option>
    <option value="geoLarrivee">geoLarrivee</option>
    <option value="geoLaskowski">geoLaskowski</option>
    <option value="geoLoximuthal">geoLoximuthal</option>
    <option value="geoMercator" selected>geoMercator</option>
    <option value="geoMiller">geoMiller</option>
    <option value="geoMollweide">geoMollweide</option>
    <option value="geoMtFlatPolarParabolic">geoMtFlatPolarParabolic</option>
    <option value="geoMtFlatPolarQuartic">geoMtFlatPolarQuartic</option>
    <option value="geoMtFlatPolarSinusoidal">geoMtFlatPolarSinusoidal</option>
    <option value="geoNaturalEarth1">geoNaturalEarth1</option>
    <option value="geoNaturalEarth2">geoNaturalEarth2</option>
    <option value="geoNellHammer">geoNellHammer</option>
    <option value="geoNicolosi">geoNicolosi</option>
    <option value="geoOrthographic">geoOrthographic</option>
    <option value="geoPatterson">geoPatterson</option>
    <option value="geoPeirceQuincuncial">geoPeirceQuincuncial</option>
    <option value="geoPolyconic">geoPolyconic</option>
    <option value="geoPolyhedralButterfly">geoPolyhedralButterfly</option>
    <option value="geoPolyhedralCollignon">geoPolyhedralCollignon</option>
    <option value="geoPolyhedralWaterman">geoPolyhedralWaterman</option>
    <option value="geoPolyhedralVoronoi">geoPolyhedralVoronoi</option>
    <option value="geoRectangularPolyconic">geoRectangularPolyconic</option>
    <option value="geoRobinson">geoRobinson</option>
    <option value="geoSatellite">geoSatellite</option>
    <option value="geoSinuMollweide">geoSinuMollweide</option>
    <option value="geoSinusoidal">geoSinusoidal</option>
    <option value="geoStereographic">geoStereographic</option>
    <option value="geoTetrahedralLee">geoTetrahedralLee</option>
    <option value="geoTimes">geoTimes</option>
    <option value="geoTransverseMercator">geoTransverseMercator</option>
    <option value="geoVanDerGrinten">geoVanDerGrinten</option>
    <option value="geoVanDerGrinten2">geoVanDerGrinten2</option>
    <option value="geoVanDerGrinten3">geoVanDerGrinten3</option>
    <option value="geoVanDerGrinten4">geoVanDerGrinten4</option>
    <option value="geoWagner">geoWagner</option>
    <option value="geoWagner4">geoWagner4</option>
    <option value="geoWagner6">geoWagner6</option>
    <option value="geoWagner7">geoWagner7</option>
    <option value="geoWiechel">geoWiechel</option>
    <option value="geoWinkel3">geoWinkel3</option>
  </select>
</p>

<p>
  <label>
    <input id="axialTilt" type="checkbox" checked/>
    Keep it real! Use Earth's axial tilt of ~23.4°.
  </label>
</p>

<canvas id="ortho" width="960" height="600"></canvas>
<canvas id="any" width="960" height="600"></canvas>

<p>
  Blog post:
  <a href="https://petrichor.studio/2018/06/29/map-projections-in-the-web/" target="_blank">
    "Map Projections on the Web"
  </a>
</p>

<script src="https://d3js.org/d3.v5.min.js"></script>
<script src="https://unpkg.com/d3-geo-projection@2.9.0/dist/d3-geo-projection.min.js"></script>
<script src="https://unpkg.com/d3-geo-polygon@1.11.0/dist/d3-geo-polygon.min.js"></script>
<script src="https://unpkg.com/topojson-client@3.1.0/dist/topojson-client.min.js"></script>
<script src="https://unpkg.com/topojson-simplify@3.0.3/dist/topojson-simplify.min.js"></script>
!

CSS 

              
                body {
  margin: 5px;
  text-align: center;
  font-family: sans-serif;
}

h1 {
  font-size: 1.25rem;
  margin: 7px 0;
}

p {
  font-size: 0.8rem;
}

p:first-of-type {
  font-weight: bold;
}

select#projectionChoice {
  max-width: 50vw;
  font-weight: bold;
  cursor: pointer;
}

label {
  cursor: pointer;
}

input#axialTilt {
  vertical-align: middle;
}

canvas {
  max-width: calc(50vw - 20px);
}
!

JS 

              
                var canvasAny = d3.select("canvas#any"),
  ctxAny = canvasAny.node().getContext("2d"),
  canvasAnyWidth = +canvasAny.attr("width"),
  canvasAnyHeight = +canvasAny.attr("height");

var projectionAny = d3
  .geoMercator()
  .rotate([-160, 0, -23.4])
  .fitSize([canvasAnyWidth, canvasAnyHeight], {
    type: "Sphere"
  });

var geoPathGeneratorAny = d3
  .geoPath()
  .projection(projectionAny)
  .context(ctxAny);

var canvasOrtho = d3.select("canvas#ortho"),
  ctxOrtho = canvasOrtho.node().getContext("2d"),
  canvasOrthoWidth = +canvasOrtho.attr("width"),
  canvasOrthoHeight = +canvasOrtho.attr("height");

var projectionOrtho = d3
  .geoOrthographic()
  .rotate([-160, 0, -23.4])
  .fitSize([canvasOrthoWidth, canvasOrthoHeight], {
    type: "Sphere"
  });

var geoPathGeneratorOrtho = d3
  .geoPath()
  .projection(projectionOrtho)
  .context(ctxOrtho);

var selectElement = document.querySelector("select#projectionChoice");
selectElement.addEventListener("change", function(evt) {
  changeProjection(evt.target.value);
});

var axialTilt = -23.4;

var axialTiltElement = document.querySelector("input#axialTilt");
axialTiltElement.addEventListener("change", function(evt) {
  changeAxialTilt(evt.target.checked);
});

var geoCircles = {
  type: "GeometryCollection",
  geometries: []
};

for (var longitude = -180; longitude < 180; longitude += 15) {
  for (var latitude = -90; latitude <= 90; latitude += 15) {
    geoCircles.geometries.push(
      d3
        .geoCircle()
        .center([longitude, latitude])
        .radius(1.333)()
    );
  }
}

drawSphereAndCircles(geoCircles);

d3
  .json("https://unpkg.com/world-atlas@1.1.4/world/110m.json")
  .then(function(loadedTopoJson) {
    var topology = topojson.presimplify(loadedTopoJson);
    topology = topojson.simplify(topology, 1.1);
    var worldGeoJson = topojson.feature(
      topology,
      topology.objects.land
    );

    d3.timer(function(elapsed) {
      geoPathGeneratorAny
        .projection()
        .rotate([elapsed * 0.0075 - 160, 0, axialTilt]);

      geoPathGeneratorOrtho
        .projection()
        .rotate([elapsed * 0.0075 - 160, 0, axialTilt]);

      ctxOrtho.clearRect(0, 0, canvasOrthoWidth, canvasOrthoHeight);
      ctxAny.clearRect(0, 0, canvasAnyWidth, canvasAnyHeight);

      drawWorld(worldGeoJson);

      drawSphereAndCircles(geoCircles);
    });

    var totalOptions = selectElement.options.length;
    var intervalTimer = d3.interval(function() {
      if (selectElement.selectedIndex === totalOptions - 1) {
        selectElement.selectedIndex = 1;
      } else {
        selectElement.selectedIndex++;
      }
      selectElement.dispatchEvent(new Event("change"));
    }, 2500);

    selectElement.addEventListener("focus", function() {
      intervalTimer.stop();
    });
  });

function drawWorld(worldGeoJson) {
  ctxOrtho.beginPath();
  ctxOrtho.fillStyle = "#b2df8a";
  geoPathGeneratorOrtho(worldGeoJson);
  ctxOrtho.fill();
  ctxOrtho.closePath();

  ctxAny.beginPath();
  ctxAny.fillStyle = "#b2df8a";
  geoPathGeneratorAny(worldGeoJson);
  ctxAny.fill();
  ctxAny.closePath();
}

function drawSphereAndCircles(geoCircles) {
  ctxOrtho.beginPath();
  ctxOrtho.fillStyle = "#1f78b4";
  geoPathGeneratorOrtho(geoCircles);
  ctxOrtho.fill();
  ctxOrtho.closePath();

  ctxOrtho.beginPath();
  ctxOrtho.strokeStyle = "#1f78b4";
  geoPathGeneratorOrtho({ type: "Sphere" });
  ctxOrtho.stroke();
  ctxOrtho.closePath();

  ctxAny.beginPath();
  ctxAny.fillStyle = "#1f78b4";
  geoPathGeneratorAny(geoCircles);
  ctxAny.fill();
  ctxAny.closePath();

  ctxAny.beginPath();
  ctxAny.strokeStyle = "#1f78b4";
  geoPathGeneratorAny({ type: "Sphere" });
  ctxAny.stroke();
  ctxAny.closePath();
}

function changeProjection(d3ProjectionName) {
  var newProjection = d3[d3ProjectionName]().fitSize(
    [canvasAnyWidth, canvasAnyHeight],
    {
      type: "Sphere"
    }
  );

  geoPathGeneratorAny.projection(newProjection);
}

function changeAxialTilt(checked) {
  var newAxialTilt = checked ? -23.4 + 0 : 0;

  d3
    .select({})
    .transition()
    .duration(1250)
    .ease(d3.easeBackOut)
    .tween(null, function() {
      var interpolator = d3.interpolate(axialTilt, newAxialTilt);
      return function(t) {
        axialTilt = interpolator(t);
      };
    });
}
!
999px

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