我有一个关于 D3 制图的问题。我正在做一个小项目，我是 D3 的新手。
我已经从这个例子开始：http ://bl.ocks.org/mbostock/5914438 而不是显示状态网格，我想在地图上的某些位置（经度/纬度）显示圆圈。我目前面临的问题是圆圈不在地图上的正确位置。我怀疑问题在于迈克使用的特殊投影。他使用 1x1 方形投影。可能这是显示瓷砖所必需的。当我投影坐标时，值都在-1和1之间。我想我可以通过将宽度乘以高度和宽度来修复它，但它不起作用。下面是我的代码（代码段没有运行，因为它缺少文件）。感谢您的帮助！
<!DOCTYPE html>
<meta charset="utf-8">
<style>
body {
margin: 0;
}
path {
fill: none;
stroke: red;
stroke-linejoin: round;
stroke-width: 1.5px;
}
circle {
fill: #fff;
fill-opacity: 0.4;
stroke: #111;
}
</style>
<svg>
</svg>
<script src="//d3js.org/d3.v4.min.js"></script>
<script src="//d3js.org/d3-tile.v0.0.min.js"></script>
<script src="//d3js.org/topojson.v1.min.js"></script>
<script>
var pi = Math.PI,
tau = 2 * pi;
var width = Math.max(960, window.innerWidth),
height = Math.max(500, window.innerHeight);
// Initialize the projection to fit the world in a 1×1 square centered at the origin.
var projection = d3.geoMercator()
.scale(1 / tau)
.translate([0, 0]);
var path = d3.geoPath()
.projection(projection);
var tile = d3.tile()
.size([width, height]);
var zoom = d3.zoom()
.scaleExtent([1 << 9, 1 << 23])
.on("zoom", zoomed);
var svg = d3.select("svg")
.attr("width", width)
.attr("height", height);
var raster = svg.append("g");
var vector = svg.append("path");
var circle = svg.append("g")
d3.json("/data/flyingsites/AD.json", function(error, flyingsites) {
if (error) console.log(error);
// Compute the projected initial center.
var center = projection([6.2, 45.8]);//45,809718, 6,252314
// Apply a zoom transform equivalent to projection.{scale,translate,center}.
svg
.call(zoom)
.call(zoom.transform, d3.zoomIdentity
.translate(width / 2, height / 2)
.scale(1 << 12)
.translate(-center[0], -center[1]));
//add flying sites
circle.selectAll("circle")
.data(flyingsites.features)
.enter().append("circle")
.attr('r',5)
.attr('cx',function(d) { return projection(d.geometry.coordinates)[0]*width})
.attr('cy',function(d) { return projection(d.geometry.coordinates)[1]*height})
.style('fill','red')
//console.log(flyingsites.features);
//console.log(circle);
});
function zoomed() {
var transform = d3.event.transform;
var tiles = tile
.scale(transform.k)
.translate([transform.x, transform.y])
();
vector
.attr("transform", transform)
.style("stroke-width", 1 / transform.k);
circle
.attr("transform", "translate(" + transform.x + "," + transform.y + ")");
var image = raster
.attr("transform", stringify(tiles.scale, tiles.translate))
.selectAll("image")
.data(tiles, function(d) { return d; });
image.exit().remove();
image.enter().append("image")
.attr("xlink:href", function(d) { return "http://" + "abc"[d[1] % 3] + ".tile.openstreetmap.org/" + d[2] + "/" + d[0] + "/" + d[1] + ".png"; })
.attr("x", function(d) { return d[0] * 256; })
.attr("y", function(d) { return d[1] * 256; })
.attr("width", 256)
.attr("height", 256);
}
function stringify(scale, translate) {
var k = scale / 256, r = scale % 1 ? Number : Math.round;
return "translate(" + r(translate[0] * scale) + "," + r(translate[1] * scale) + ") scale(" + k + ")";
}
</script>