那里的投影路径;但路径只有1px乘1px？

Question

我正在尝试投影一个geojson文件，它有一个默认的投影类型。

我的路径线出现在控制台检查器中：

但这些行只有1px by 1px，因此它们不会出现。发生了什么事？

我的代码：

var mapWidth = 60;
var mapHeight = 90;

var projection = d3.geo.mercator().scale([100]);
var path = d3.geo.path()
    .projection(projection);


(function run() { 
    d3.json("./data/output.geojson", function(error, map) {

  var chart = d3.select("#charts").selectAll("svg")
           .data(map.features)
           .enter()
           .append("svg")
               .attr("width", mapWidth)
               .attr("height", mapHeight)
               .append("g")

              chart
                .append("path")
                .attr("d", path)
                .style("fill","steelblue");
    });

})()

Geojson如下（这是一个片段）：

{
"type": "FeatureCollection",
"crs": { "type": "name", "properties": { "name": "urn:ogc:def:crs:OGC:1.3:CRS84" } },

"features": [
{ "type": "Feature", "properties": { "neighborhood": "Battery Park City", "boroughCode": "1", "borough": "Manhattan", "@id": "http:\/\/nyc.pediacities.com\/Resource\/Neighborhood\/Battery_Park_City" }, "geometry": { "type": "Polygon", "coordinates": [ [ [ -74.013754000000176, 40.71369 ], [ -74.014262000000187, 40.710928000000195 ], [ -74.016542000000186, 40.704733000000275 ], [ -74.016174, 40.702572000000174 ], [ -74.01563, 40.701862000000233 ], [ -74.015127, 40.701390000000259 ], [ -74.014008, 40.701043000000325 ], [ -74.013959214170356, 40.700965860994032 ], [ -74.01410490300087, 40.700510828386832 ], [ -74.