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Google Maps + D3
<!DOCTYPE html>
<meta name="viewport" content="initial-scale=1.0, user-scalable=no"/>
<script type="text/javascript" src=""></script>
<script type="text/javascript" src=""></script>
<style type="text/css">
html, body, #map {
width: 100%;
height: 100%;
margin: 0;
padding: 0;
.stations, .stations svg {
position: absolute;
.stations svg {
width: 60px;
height: 20px;
padding-right: 100px;
font: 10px sans-serif;
.stations circle {
fill: brown;
stroke: black;
stroke-width: 1.5px;
<div id="map"></div>
<script type="text/javascript">
// Create the Google Map…
var map = new google.maps.Map("#map").node(), {
zoom: 8,
center: new google.maps.LatLng(37.76487, -122.41948),
mapTypeId: google.maps.MapTypeId.TERRAIN
// Load the station data. When the data comes back, create an overlay.
d3.json("stations.json", function(data) {
var overlay = new google.maps.OverlayView();
// Add the container when the overlay is added to the map.
overlay.onAdd = function() {
var layer ="div")
.attr("class", "stations");
// Draw each marker as a separate SVG element.
// We could use a single SVG, but what size would it have?
overlay.draw = function() {
var projection = this.getProjection(),
padding = 10;
var marker = layer.selectAll("svg")
.each(transform) // update existing markers
.attr("class", "marker");
// Add a circle.
.attr("r", 4.5)
.attr("cx", padding)
.attr("cy", padding);
// Add a label.
.attr("x", padding + 7)
.attr("y", padding)
.attr("dy", ".31em")
.text(function(d) { return d.key; });
function transform(d) {
d = new google.maps.LatLng(d.value[1], d.value[0]);
d = projection.fromLatLngToDivPixel(d);
.style("left", (d.x - padding) + "px")
.style("top", (d.y - padding) + "px");
// Bind our overlay to the map…
{"KMAE":[-120.12,36.98,"MADERA MUNICIPAL AIRPORT",[26,1,2,5,6,3,2,1,2,7,29,12,3]],"KSJC":[-121.92,37.37,"SAN JOSE INTERNATIONAL AIRPORT",[28,1,1,1,6,10,5,3,2,4,14,21,7]],"KMCE":[-120.50,37.28,"MERCED MUNICIPAL AIRPORT",[29,1,1,3,7,5,2,1,3,6,12,26,5]],"KMER":[-120.57,37.37,"Merced / Castle Air Force Base",[34,1,1,1,4,5,2,1,1,4,17,22,7]],"KAPC":[-122.28,38.20,"NAPA COUNTY AIRPORT",[23,2,1,6,3,3,8,18,11,13,4,3,5]],"KSUU":[-121.95,38.27,"Fairfield / Travis Air Force Base",[13,7,4,3,3,6,4,13,33,4,1,2,7]],"KSQL":[-122.25,37.52,"San Carlos Airport",[18,3,2,2,3,4,3,2,5,17,16,12,12]],"KSNS":[-121.60,36.67,"SALINAS MUNICIPAL AIRPORT",[21,1,1,6,12,3,1,2,9,21,17,5,1]],"KMOD":[-120.95,37.62,"MODESTO CITY CO SHAM FLD",[27,1,1,2,10,5,1,1,1,3,17,24,8]],"KOAK":[-122.23,37.72,"METRO OAKLAND INTERNATIONAL AIRPORT ",[16,3,3,2,4,6,3,4,9,23,20,6,2]],"KSCK":[-121.23,37.90,"STOCKTON METROPOLITAN AIRPORT ",[21,2,2,3,6,8,2,1,4,15,19,12,4]],"KCCR":[-122.05,38.00,"CONCORD BUCHANAN FIELD",[24,3,2,1,1,5,17,12,9,9,7,6,4]],"KMRY":[-121.85,36.58,"MONTEREY PENINSULA AIRPORT",[26,1,2,9,5,3,4,9,13,14,9,4,1]],"KPAO":[-122.12,37.47,"Palo Alto Airport",[31,3,1,1,2,5,1,1,1,4,10,25,14]],"KSAC":[-121.50,38.50,"SACRAMENTO EXECUTIVE AIRPORT ",[32,1,0,1,3,11,12,16,5,2,4,9,3]],"KHWD":[-122.12,37.67,"HAYWARD AIR TERMINAL",[20,2,7,2,2,6,3,3,6,23,18,6,2]],"KSTS":[-122.82,38.50,"SANTA ROSA SONOMA COUNTY",[46,1,0,1,5,13,10,4,3,3,4,6,3]],"KSMF":[-121.60,38.70,"SACRAMENTO INTERNATIONAL AIRPORT",[19,2,1,2,4,21,18,8,3,2,5,12,4]],"KNUQ":[-122.05,37.43,"MOFFETT FIELD",[35,3,1,1,4,7,2,1,2,5,6,17,15]],"KRHV":[-121.82,37.33,"San Jose / Reid / Hillv",[35,0,0,1,4,4,2,1,1,10,28,11,1]],"KWVI":[-121.78,36.93,"WATSONVILLE MUNICIPAL AIRPORT ",[44,1,2,3,4,5,7,9,8,4,6,5,2]],"KMHR":[-121.30,38.55,"Sacramento, Sacramento Mather Airport",[21,1,1,2,8,15,12,12,7,4,5,7,3]],"KVCB":[-121.95,38.38,"VACAVILLE NUT TREE AIRPORT",[36,2,1,1,2,6,10,18,10,2,2,5,6]],"KSFO":[-122.37,37.62,"SAN FRANCISCO INTERNATIONAL AIRPORT ",[13,3,3,2,3,4,4,4,7,31,20,2,3]],"KLVK":[-121.82,37.70,"LIVERMORE MUNICIPAL AIRPORT ",[32,2,7,3,1,1,2,7,9,17,16,2,1]]}
bsn commented

Hi, you have issue when building svg:circle, so it doesn't work in Firefox and all spots has wrong coordinates(because of padding inside the svg element). I forked your gist and made changes so you can take a look and make changes in your code if you want.


Thanks, updated!


Very cool, just what I was looking for. <3 d3!

Unknown commented

Thanks. This is awesome!!


Marvellous. I've attempted an adaption which uses geocoding to position the markers

Console log shows the geo function is pulling six lat/lon figures. The problem is that it is not attaching each lat/long to each marker, even though the transform function (should be) passed the right data.

Is it the case the the geo function is running 6 times, then passing the final amount to a single marker? If so, how can this be changed?

I am developing my JS skills as the code probably shows, much appreciation in advance of any help.


Here's a fork that shows how to use d3.geo machinery to draw geographic objects into the google overlay layer, including correct clipping etc.


How might I size each dot based on a value in the json? If I added another key : value pair to each object, how can this be selected for binding to the circle elements?

Me example data is below. I'm having some difficulty binding this data in lieu of the set used to create the example. What I'm trying to do is use the lat/long for location as the example does, but bind the value for all "in" values to the size of each circle.

Any help is much appreciated, thanks!

"Montebello/19th Ave":[-112.099655,33.520002],
"in": 895666,
"out": 913526
"19th Ave/Camelback Rd":[-112.09958,33.509661],
"in": 496179,
"out": 483762
"7th Ave/Camelback Rd":[-112.082757,33.509304],
"in": 285608,
"out": 297610


@mickdee: Sounds like you have two questions here so I'll answer them separately.

First, to do data binding for your sample set instead of

      var marker = layer.selectAll("svg")

you'll want to do

      var marker = layer.selectAll("svg")

because you have an array of objects where Mike had everything as properties of a top-level object. (NB: this also assumes that your data is in a separate "stations.json" file in your root directory; there are a few more lines to change if you have it somewhere else.) You will also need to change the line

d = new google.maps.LatLng(d.value[1], d.value[0])

but with your current layout I can't think of a way to do it that doesn't seem ugly and computationally wasteful. If your objects were instead something like

"name": "Montebello/19th Ave",
"location": [-112.099655,33.520002],
"in": 895666,
"out": 913526

then you could do

d = new google.maps.LatLng(d.location[1], d.location[0])

As for making the radius correspond to the data, you should be able to swap out

.attr("r", 4.5)

with something like

.attr("r", function(d) {return / 10000;})

(the 10000 is an arbitrary number to make the circles reasonable; tweak as needed).
I'm doing something similar and running into a problem with circles not showing up until I zoom in or out -- still trying to figure out what's going on there. But hopefully this gets you pointed in the right direction.


This is a great example, but I really want to make it interactive and I can't figure out how to register click events with this. I'm not sure if the google map is eating them or something, but I'm stuck. My d3 approach was

marker.on('click', function(d,i){

inside overlay.onAdd, but I'm getting nothing in the console when I click. Similar results setting up listeners with or jQuery.

Any suggestions?


Thanks for the great help nickbenes! I've made some progress with dots sized and colored according to data values for each station.

I've also got click events working to swap in new values for each station. The output to a user should look fine, but behind the scenes I'm doing this pretty sloppily at the moment.

Check out the example here:

And the code here:

My next task is getting tooltips to work. I've tried just about every way I can think of but can't successfully get mouseover events to work properly on the svg circles either with d3 or plain ol' css.



I am new here so please accept my apologizes in advance if I am asking something wrongly. If possible I would like to ask you for help, I am using the code above in this article to plot two set of circles in a google map with some variations, so I am getting the two sets from two different files, for that I am using 2 overlays, that are added to the map separately, but it is plotting only the first set of circles, if possible could I post my code and the two files anywhere to get any help with that?

Thank you in advance.


Has a solution been found for this mouse event problem? I also would like to create some more interaction with my graphs.


I've implemented this and the marker shows up. However, when zooming in and out, the marker doesn't update its position (though panning works just fine). Any hint?

cc @mbostock


ah, nm, it turns out some css style is needed. In my case, this was needed:

.stations, .stations svg {
  position: absolute;

any examples on how to add d3 circles in real time as data is received?


I, too, am looking for a solution to mouseover/onclick events for the svg circles. Anyone found anything?


I ended up answering my own question. You have to make a couple changes. First make the overlayLayer an overlayMouseTarget like so:

var layer ="div")
.attr("class", "stations");

I added the following attr to the circle:

marker.append("svg:circle").attr("r", 4.5).attr("cx", padding).attr("cy", padding).on("click",toggleExpand);

...and then had to define the toggleExpand() method:

function toggleExpand() {
if("r") == 4.5) {"r",7)
} else {"r",4.5)

(please forgive the formatting, I can't make the function look good)


Thanks for this example it got me heading in the right direction.

I copied it (didn't fork) and made some changes for my own purposes so that I could use a single SVG instead of one per map marker and like several others mentioned so I could have my markers get mouse events (using overlayMouseTarget instead of overlayLayer.

I did a small writeup of my changes here and the end result is here.


I've already loaded data from Elasticsearch, doing a query to ES, into an object called "resp"... I've this values:

"hits": {
"hits": [
"_source": {"location": "43.54526,-5.661926"},
"_source": {"location": "40.41669,-3.700346"}

so values from "resp.hits.hits._source.location" is what i want to draw in the map

I've tried to adapt the code with

var marker = layer.selectAll("svg")


d = new google.maps.LatLng(d.location)
d = new google.maps.LatLng(d.location[1],d.location[0])

It doens't works ¿? Thanks!

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