Based on http://bl.ocks.org/mbostock/899711 which uses D3 to draw elements into a google maps overlay layer, but doesn't use d3.geo machinery to draw map geometry. This gist illustrates how to align a D3 mercator projection with google maps so we can do standard d3 mapping stuff on top of the google API.
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November 22, 2019 18:46
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Illustrate embedding geojson/topojson geometry into a google maps overlay using d3.geo.projection.
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| <!DOCTYPE html> | |
| <html> | |
| <head> | |
| <meta name="viewport" content="initial-scale=1.0, user-scalable=no"/> | |
| <script type="text/javascript" src="http://maps.google.com/maps/api/js?sensor=true"></script> | |
| <script type="text/javascript" src="http://d3js.org/d3.v3.min.js"></script> | |
| <script type="text/javascript" src="http://d3js.org/queue.v1.min.js"></script> | |
| <script src="http://d3js.org/topojson.v1.min.js"></script> | |
| <style type="text/css"> | |
| html, body { | |
| width: 100%; | |
| height: 100%; | |
| margin: 0; | |
| padding: 0; | |
| } | |
| #map { | |
| margin: 0; | |
| padding: 0; | |
| } | |
| #d3map { | |
| /*pointer-events: none;*/ | |
| -webkit-transform: none; | |
| position: relative; | |
| top: 0px; | |
| left: 0px; | |
| } | |
| #countries path { | |
| stroke-width: 1px; | |
| vector-effect: non-scaling-stroke; | |
| fill: none; | |
| stroke: #333; | |
| } | |
| </style> | |
| </head> | |
| <body> | |
| <script type="text/javascript"> | |
| var width = 600, | |
| height = 400, | |
| div = d3.select('body') | |
| .append('div') | |
| .attr('id','map') | |
| .style('width', width + 'px') | |
| .style('height', height + 'px'); | |
| // Create the Google Map… | |
| var map = new google.maps.Map(div.node(), { | |
| zoom: 2, | |
| center: new google.maps.LatLng(37.76487, -122.41948), | |
| mapTypeId: google.maps.MapTypeId.TERRAIN, | |
| minZoom: 2 // stuff goes wrong if we allow world wraparound | |
| }); | |
| // Load the data. When the data comes back, create an overlay. | |
| queue() | |
| .defer(d3.json, "world-110m.json") | |
| .await(ready); | |
| var svg, overlay; | |
| function ready(error, world) { | |
| var countries = topojson.feature(world, world.objects.countries).features, | |
| land = topojson.feature(world, world.objects.land); | |
| overlay = new google.maps.OverlayView(); | |
| overlay.onAdd = function() { | |
| // create an SVG over top of it. | |
| svg = d3.select(overlay.getPanes().overlayLayer) | |
| .append('div') | |
| .attr('id','d3map') | |
| .style('width', width + 'px') | |
| .style('height', height + 'px') | |
| .append('svg') | |
| .attr('width', width) | |
| .attr('height', height); | |
| svg.append('g') | |
| .attr('id','countries') | |
| .selectAll('path') | |
| .data(countries) | |
| .enter().append('path') | |
| .attr('class','country'); | |
| overlay.draw = redraw; | |
| google.maps.event.addListener(map, 'bounds_changed', redraw); | |
| google.maps.event.addListener(map, 'center_changed', redraw); | |
| }; | |
| overlay.setMap(map); | |
| } | |
| function redraw() { | |
| var bounds = map.getBounds(), | |
| ne = bounds.getNorthEast(), | |
| sw = bounds.getSouthWest(), | |
| projection = d3.geo.mercator() | |
| .rotate([-bounds.getCenter().lng(),0]) | |
| .translate([0,0]) | |
| //.center([0,0]) | |
| .scale(1), | |
| path = d3.geo.path() | |
| .projection(projection); | |
| var p1 = projection([ne.lng(),ne.lat()]), | |
| p2 = projection([sw.lng(),sw.lat()]); | |
| svg.select('#countries').attr('transform', | |
| 'scale('+width/(p1[0]-p2[0])+','+height/(p2[1]-p1[1])+')'+ | |
| 'translate('+(-p2[0])+','+(-p1[1])+') '); | |
| svg.selectAll('path').attr('d', path); | |
| } | |
| </script> | |
| </body> | |
| </html> |
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I'm also noticing an issue with panning. The overlay layer moves at a different scale than the underlaying map, so it "floats" on top of it. Any idea what might fix this?