d3.geo buffer around a feature

问题

Is it possible to draw a buffer (another feature) around a geographic feature in d3.js as a fixed distance unit (kilometers or miles)?

For instance, how would I draw a path around a point that extends 25 miles from that point in every direction. I've tried using d3.geo.circle and passing a fraction of degree (25 miles / approximately 69 miles per latitudinal degree or 25 / 69) but realize that although d3.geo.circle handles the reprojection of degrees, it does not accommodate for the differing lengths of each longitudinal degrees.

buffer = d3.geo.circle().angle(25/69).origin(function(x, y) { return [x, y]; })

I'm borrowing from this:

http://bl.ocks.org/mbostock/5628479

Update:

It looks like what I'd like to do is create a geodesic buffer.

Update:

I was able to create the buffer by drawing a path from a series of destination points given a distance and bearing from a start point.

See http://www.movable-type.co.uk/scripts/latlong.html for JavaScript implementation

Like this:

function drawBuffer(lat, long, distance){
    var intervals = 18;
    var intervalAngle = (360 / intervals);
    var pointsData = [];
    for(var i = 0; i < intervals; i++){
        pointsData.push(getDestinationPoint(lat, long, i * intervalAngle, distance));
    }
    // Draw path using pointsData;
}

回答1:

AFAIK doing this in D3 itself would be quite painful, as it's not really meant to create/modify features. I would recommend doing this as a preprocessing step in a GIS program such as QGIS, which allows you to buffer features in a number of ways. From there, you can export as GeoJSON and use with D3 in the usual way.

回答2:

I was able to create a buffer around a point by drawing a path from a series of destination points given a distance and bearing from a start point.

See http://www.movable-type.co.uk/scripts/latlong.html for JavaScript implementation

Like this:

function drawBuffer(lat, long, distance){
    var intervals = 18;
    var intervalAngle = (360 / intervals);
    var pointsData = [];
    for(var i = 0; i < intervals; i++){
        pointsData.push(getDestinationPoint(lat, long, i * intervalAngle, distance)); // See link
    }
    // Draw path using pointsData;
}

来源：https://stackoverflow.com/questions/20130186/d3-geo-buffer-around-a-feature