Swiss Cantons & Lakes

This example shows how to create canton boundaries consistent with lake boundaries using topojson-merge. To avoid losing information, --no-quantization is used when creating the initial unmerged topologies. Data from interactivethings/swiss-maps.

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

.boundary {
  fill: none;
  stroke: #fff;
  stroke-linejoin: round;
  stroke-linecap: round;
}

.feature--canton {
  fill: #bbb;
}

.feature--lake {
  fill: steelblue;
  fill-opacity: .8;
}

.feature :hover {
  fill: orange;
}

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

var width = 960,
    height = 500;

var color = d3.scale.category20c();

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

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

d3.json("ch.json", function(error, ch) {
  if (error) throw error;

svg.append("g")
      .attr("class", "feature feature--canton")
    .selectAll("path")
      .data(topojson.feature(ch, ch.objects.cantons).features)
    .enter().append("path")
      .attr("d", path);

svg.append("g")
      .attr("class", "feature feature--lake")
    .selectAll("path")
      .data(topojson.feature(ch, ch.objects.lakes).features)
    .enter().append("path")
      .attr("d", path);

svg.append("path")
      .datum(topojson.mesh(ch, ch.objects.cantons, function(a, b) { return a !== b; }))
      .attr("class", "boundary boundary--cantons")
      .style("stroke-width", "1px")
      .attr("d", path);
});

</script>

https://d3js.org/d3.v3.min.js

https://d3js.org/topojson.v1.min.js