Airy’s Minimum Error by mbostock

index.html

<!DOCTYPE html>
<meta charset="utf-8">
<style>

.graticule {
  fill: none;
  stroke: #777;
  stroke-width: .5px;
  stroke-opacity: .5
}

.land {
  fill: #ddd;
}

.countries {
  fill: #222;
}

.boundary {
  fill: none;
  stroke: #fff;
  stroke-width: .5px;
}

</style>
<body>
<script src="//d3js.org/d3.v3.min.js"></script>
<script src="//d3js.org/d3.geo.projection.v0.min.js"></script>
<script src="//d3js.org/topojson.v1.min.js"></script>
<script>

var width = 960,
    height = 640;

// //en.wikipedia.org/wiki/ISO_3166-1_numeric
var ids = {840: 1, 484: 1, 124: 1, 630: 1};

var projection = d3.geo.airy()
    .rotate([105, -45])
    .center([-3, 5])
    .scale(560)
    .translate([width / 2, height / 2])
    .precision(.1)
    .clipAngle(70);

// Compute radius from viewport height. TODO Make automatic.
projection
    .radius(projection.invert([width / 2, 0])[1] - projection.invert([width / 2, height])[1]);

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

var graticule = d3.geo.graticule();

var svg = d3.select("body").append("svg")
    .attr("width", width)
    .attr("height", height);

svg.append("path")
    .datum(graticule)
    .attr("class", "graticule")
    .attr("d", path);

d3.json("/mbostock/raw/4090846/world-50m.json", function(error, world) {
  if (error) throw error;

  svg.insert("path", ".graticule")
      .datum(topojson.feature(world, world.objects.land))
      .attr("class", "land")
      .attr("d", path);

  svg.insert("path", ".graticule")
      .datum(topojson.feature(world, {type: "GeometryCollection", geometries: world.objects.countries.geometries.filter(function(d) { return d.id in ids; })}))
      .attr("class", "countries")
      .attr("d", path);

  svg.insert("path", ".graticule")
      .datum(topojson.mesh(world, world.objects.countries, function(a, b) { return a !== b; }))
      .attr("class", "boundary")
      .attr("d", path);
});

d3.select(self.frameElement).style("height", height + "px");

</script>