获取 OpenLayers 中 2 个 LonLat 对象之间的距离（以像素为单位）

发布于 2024-11-18 17:39:15 字数 698 浏览 1 评论 0原文

我有 2 个 OpenLayers.LonLat 对象，我想确定这两个对象之间当前缩放的像素距离。我使用 OpenLayers.Layer.getViewPortPxFromLonLat() 来确定点的 x 和 y，然后减去以查看两者之间的差异，但对于相距 2000 公里的点，我得到的值非常小。

这是我的代码：

        var center_lonlat = new OpenLayers.LonLat(geometry.lon, geometry.lat);
        var center_px = layer.getViewPortPxFromLonLat(center_lonlat);

        var radius_m = parseFloat(feature.attributes["radius"]);
        var radius_lonlat = OpenLayers.Util.destinationVincenty(center_lonlat, 0, radius_m);
        var radius_px = layer.getViewPortPxFromLonLat(radius_lonlat);

        var radius = radius_px.y - center_px.y;

我试图在这里画一个圆，因为我收到了一个中心点和以米为单位的半径。 LonLat 对象似乎没问题。

我做错了什么吗？

原文

I have 2 OpenLayers.LonLat objects, and I want to determine the distance in pixels for the current zoom between the 2. I'm using OpenLayers.Layer.getViewPortPxFromLonLat() to determine the x and y of the points and then subtract to see the difference between the 2, but the values that I get are very small for points that are 2000km apart.

Here is my code:

        var center_lonlat = new OpenLayers.LonLat(geometry.lon, geometry.lat);
        var center_px = layer.getViewPortPxFromLonLat(center_lonlat);

        var radius_m = parseFloat(feature.attributes["radius"]);
        var radius_lonlat = OpenLayers.Util.destinationVincenty(center_lonlat, 0, radius_m);
        var radius_px = layer.getViewPortPxFromLonLat(radius_lonlat);

        var radius = radius_px.y - center_px.y;

I'm trying here to draw a circle, giving that I receive a center point and a radius in meters. The LonLat object seems to be ok.

Am I doing something wrong ?

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与他有关 2024-11-25 17:39:15

我发现了问题：destinationVincenty() 需要并返回 wgs84 中的坐标，其中我的地图使用球面墨卡托投影。

我希望我得到了正确的答案，因为投影让我头晕，从来没有真正理解它们:(。我在控制台中查找我的坐标的数字以及用于计算 getViewPortPxFromLonLat 的 map.getExtent() 的坐标()，我意识到它们的数量级不正确，然后我就明白了，

所以，代码现在是：

        var spherical_mercator = new OpenLayers.Projection("EPSG:900913");
        var wgs84 = new OpenLayers.Projection("EPSG:4326");

        var map = feature.layer.map;
        var geometry = feature.geometry;
        var center_lonlat = new OpenLayers.LonLat(geometry.y, geometry.x);
        var center_px = map.getViewPortPxFromLonLat(center_lonlat);

        var radius_m = parseFloat(feature.attributes["radius"]);
        var radius_lonlat = OpenLayers.Util.destinationVincenty(center_lonlat.clone().transform(spherical_mercator, wgs84), 0, radius_m).transform(wgs84, spherical_mercator);
        var radius_px = map.getViewPortPxFromLonLat(radius_lonlat);

        var radius = Math.abs(radius_px.y - center_px.y);

用 OpenLayers.Control.ScaleLine 测量圆圈，尺寸是准确的。：D

I found the issue: destinationVincenty() need and returns coordinates in wgs84 where my map was using spherical mercator projection.

I hope I got correctly the answer, because projections make me dizzy and never really understood them :(. I was looking in the console to the numbers for my coordinates and the coordinates from the map.getExtent() that is used to calculate the getViewPortPxFromLonLat() and I realised they are not in the right order of magnitude, and then it hit me.

So, the code is now:

        var spherical_mercator = new OpenLayers.Projection("EPSG:900913");
        var wgs84 = new OpenLayers.Projection("EPSG:4326");

        var map = feature.layer.map;
        var geometry = feature.geometry;
        var center_lonlat = new OpenLayers.LonLat(geometry.y, geometry.x);
        var center_px = map.getViewPortPxFromLonLat(center_lonlat);

        var radius_m = parseFloat(feature.attributes["radius"]);
        var radius_lonlat = OpenLayers.Util.destinationVincenty(center_lonlat.clone().transform(spherical_mercator, wgs84), 0, radius_m).transform(wgs84, spherical_mercator);
        var radius_px = map.getViewPortPxFromLonLat(radius_lonlat);

        var radius = Math.abs(radius_px.y - center_px.y);

Measured the circles with the OpenLayers.Control.ScaleLine, and the size is dead on :D

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