Projection explorer

Projection explorer.

forked from d3indepth's block: Projection explorer

<!DOCTYPE html>
<meta charset="utf-8">
<head>
  <title>Geo (projection configuration)</title>
</head>

#description {
  margin: 20px 0;
  font-size: 16px;
  line-height: 24px;
  color: #555;
}

#menu {
  position: absolute;
  top: 20px;
  left: 30px;
}

#menu .item {
  margin-bottom: 12px;
}

#menu .item input {
  width: 100px;
}

#menu select {
  margin-top: 4px;
}

#menu .item .value {
  font-weight: bold;
}

#menu .item span, #menu .item input {
  vertical-align: middle;
}

#menu .item .low {
  display: inline-block;
  width: 30px;
  text-align: right;
}

svg {
  border: 1px solid #eee;
}

.map path {
  fill: #45716a;
  stroke: #777;
}

.projection-center {
  fill: red;
}

.graticule path {
  fill: none;
  stroke: #eee;
}

.circles path {
  fill: none;
  stroke: #aaa;
}
</style>

<body>
  <div id="menu">
    <div class="projection-type item">
      <div><select name="type" value="150"></select></div>
    </div>
    <div class="slider item">
      <div class="label">scale (<span class="value">120</span>)</div>
      <div><span class="low">0</span> <input type="range" name="scale" min="0" max="400" value="120"> <span>400</span></div>
    </div>
    <div class="slider item">
      <div class="label">translate (x) (<span class="value">480</span>)</div>
      <div><span class="low">0</span> <input type="range" name="translateX" min="0" max="960" value="480"> <span>960</span></div>
    </div>
    <div class="slider item">
      <div class="label">translate (y) (<span class="value">250</span>)</div>
      <div><span class="low">0</span> <input type="range" name="translateY" min="0" max="500" value="250"> <span>500</span></div>
    </div>
    <div class="slider item">
      <div class="label">center (lon) (<span class="value">0</span>)</div>
      <div><span class="low">-180</span> <input type="range" name="centerLon" min="-180" max="180" value="0"> <span>180</span></div>
    </div>
    <div class="slider item">
      <div class="label">center (lat) (<span class="value">0</span>)</div>
      <div><span class="low">-90</span> <input type="range" name="centerLat" min="-90" max="90" value="0"> <span>90</span></div>
    </div>
    <div class="slider item">
      <div class="label">rotate (&lambda;) (<span class="value">0</span>)</div>
      <div><span class="low">-180</span> <input type="range" name="rotateLambda" min="-180" max="180" value="0"> <span>180</span></div>
    </div>
    <div class="slider item">
      <div class="label">rotate (&phi;) (<span class="value">0</span>)</div>
      <div><span class="low">-180</span> <input type="range" name="rotatePhi" min="-180" max="180" value="0"> <span>180</span></div>
    </div>
    <div class="slider item">
      <div class="label">rotate (&gamma;) (<span class="value">0</span>)</div>
      <div><span class="low">-180</span> <input type="range" name="rotateGamma" min="-180" max="180" value="0"> <span>180</span></div>
    </div>
  </div>

<div id="description">
    <div>Explore <a href="https://d3js.org/" target="_blank">D3</a>'s geographic projections and their <a href="https://github.com/d3/d3-geo/blob/master/README.md#projection_scale" target="_blank">scale</a>, <a href="https://github.com/d3/d3-geo/blob/master/README.md#projection_translate" target="_blank">translate</a>, <a href="https://github.com/d3/d3-geo/blob/master/README.md#projection_center" target="_blank">center</a> and <a href="https://github.com/d3/d3-geo/blob/master/README.md#projection_rotate" target="_blank">rotate</a> parameters. The red dot indicates the <a href="https://github.com/d3/d3-geo/blob/master/README.md#projection_center" target="_blank">projection center</a>.</div>
    <div>To demonstrate area distortion (e.g. Mercator) grey circles with the same radius have also been added.</div>
  </div>

var projection;
var geoGenerator = d3.geoPath()
  .projection(projection);

var graticule = d3.geoGraticule();

var circles = [
  [-135, 0], [-90, 0], [-45, 0], [0, 0], [45, 0], [90, 0], [135, 0], [180, 0],
  [0, -70], [0, -35], [0, 35], [0, 70],
  [180, -70], [180, -35], [180, 35], [180, 70],
];
var geoCircle = d3.geoCircle().radius(10).precision(1);

var state = {
  type: 'AzimuthalEqualArea',
  scale: 120,
  translateX: 480,
  translateY: 250,
  centerLon: 0,
  centerLat: 0,
  rotateLambda: 0.1,
  rotatePhi: 0,
  rotateGamma: 0
}

function initMenu() {
  d3.select('#menu')
    .selectAll('.slider.item input')
    .on('input', function(d) {
      var attr = d3.select(this).attr('name');
      state[attr] = this.value;
      d3.select(this.parentNode.parentNode).select('.value').text(this.value);
      update()
    });

d3.select('#menu .projection-type select')
    .on('change', function(d) {
      state.type = this.options[this.selectedIndex].value;
      update()
    })
    .selectAll('option')
    .data(projectionTypes)
    .enter()
    .append('option')
    .attr('value', function(d) {return d;})
    .text(function(d) {return d;});
}

function update() {
  // Update projection
  projection = d3['geo' + state.type]()
  geoGenerator.projection(projection);

projection
    .scale(state.scale)
    .translate([state.translateX, state.translateY])
    .center([state.centerLon, state.centerLat])
    .rotate([state.rotateLambda, state.rotatePhi, state.rotateGamma])

// Update world map
  var u = d3.select('g.map')
    .selectAll('path')
    .data(geojson.features)

u.enter()
    .append('path')
    .merge(u)
    .attr('d', geoGenerator)

// Update projection center
  var projectedCenter = projection([state.centerLon, state.centerLat]);
  d3.select('.projection-center')
    .attr('cx', projectedCenter[0])
    .attr('cy', projectedCenter[1]);

// Update graticule
  d3.select('.graticule path')
    .datum(graticule())
    .attr('d', geoGenerator);

// Update circles
  u = d3.select('.circles')
    .selectAll('path')
    .data(circles.map(function(d) {
      geoCircle.center(d);
      return geoCircle();
    }));

u.enter()
    .append('path')
    .merge(u)
    .attr('d', geoGenerator);
}

d3.json('ne_110m_land.json', function(err, json) {
  geojson = json;
  initMenu();
  update();
})

</script>
</body>
</html>

https://cdnjs.cloudflare.com/ajax/libs/d3/4.2.2/d3.min.js