geojson圈子，支持与否？

Question

当我仰望以GeoJSON的规格我看到圈的支持：

http://geopriv.dreamhosters.com/geojson/geojson-spec.html#circleExample

当我尝试在geojsonlint（http://geojsonlint.com/）的代码，但是，它给了我一个错误。

输入：

{ 
"type": "Circle", 
"coordinates": [4.884, 52.353], 
"radius": 200 
} 

给出：

"Circle" is not a valid GeoJSON type. 

我想通过使用D3，以显示与地图上的范围内的影响力的利益不同的地方。它需要GeoJson进行输入，但确实没有GeoJson支持圆圈？

Answer 1

当我仰望以GeoJSON的规格我看到圆圈支持

他们不是。似乎你设法找到一些假的或不正确的规格。去geojson.org找到specs，没有什么关于圈子的。

Answer 2

从GeoJSON的， 没有圈子的支持，但是你可以用线段形式来模拟一个圆

使用线段形式geiometry对象

"geometry": { 
     "type": "LineString", 
     "coordinates": [ 
        [center_X, center_y], 
        [center_X, center_y] 
       ] 
     } 
then set the dynamic style use radius as the strokeweight 
function featureStyle(feature){ 
    return { 
     strokeWeight: radius, 
    }; 
    } 

它看起来像在地图上的圆圈。

Answer 3

A circle... some code I use for making a circle for an OpenStreetMap 

-- x is decimal latitude 
-- y is decimal longitude 
-- r is radius -- .00010 is about 40m in OSM (3 about 50km) 

-- Adjust for map latitude distortion further north or south 

x = math.log(math.tan((90 + x) * math.pi/360))/(math.pi/180) 

-- For loop to gather all the points of circle here 1 to 360 
-- can also use the for loop to make some other interesting shapes 

for i = 1, 360 do 
    angle = i * math.pi/180 
    ptx = x + r * math.cos(angle) 
    pty = y + r * math.sin(angle) 

-- readjust latitude for map distortion 

    ptx = 180/math.pi * (2 * math.atan(math.exp(ptx * math.pi/180)) - math.pi/2) 

-- Build an array of positions for GeoJSON - formatted lat and long 

    data[i] = '[' .. string.format("%.6f",pty) .. "," 
    data[i] = data[i] .. string.format("%.6f",ptx) .. ']' 

-- End of for loop 
end 

-- Cycle through the data array with another for loop to build the 
    coordinates (put in brackets and commas etc. for the actual 
    GeoJSON coordinates string. Add data[1] to the end to close 
    the polygon (circle). A circle. 

-- If you want a solid circle then use fill and a hex color 
-- If you want a LineString just make fill invisible or #ffffff 
     Include the stroke-width and stroke-color parameters as well. 
-- If latitude is greater than 89.5 or less than -89.5 you may wish 
    to cut off the circle by drawing a line at polar regions by using 
    those latitudes. 
-- I use this simply for several circles and not for hundreds of them. 

Cheers! 
--