Two Point Equidistant by mbostock

This example demonstrates the unique property of the two-point equidistant projection: great circles centered around either of the two reference points (here Honolulu and Washington, D.C.) are projected as circles.

The projection implementation is still a work in progress, hence the visual artifacts; it requires elliptical clipping.

index.html

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

.land {
  fill: #eee;
  stroke: #444;
  stroke-width: .5px;
}

.circle {
  fill: none;
}

.circle.a {
  stroke: #f00;
}

.circle.b {
  stroke: #00a2f3;
}

</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 = 960;

var a = [-158, 21.5], // Honolulu, HI
    b = [-77, 39], // Washington, DC
    circle = d3.geo.circle();

var projection = d3.geo.twoPointEquidistant()
    .points([a, b])
    .scale(185)
    .translate([width / 2, height / 2])
    .precision(.1);

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

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

svg.append("g")
    .attr("class", "circle a")
  .selectAll("path")
    .data(d3.range(10, 180, 10))
  .enter().append("path")
    .attr("d", function(r) { return path(circle.origin(a).angle(r)()); });

svg.append("g")
    .attr("class", "circle b")
  .selectAll("path")
    .data(d3.range(10, 180, 10))
  .enter().append("path")
    .attr("d", function(r) { return path(circle.origin(b).angle(r)()); });

d3.json("/mbostock/raw/4090846/world-110m.json", function(error, world) {
  if (error) throw error;

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

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

</script>