DbGeography使圆与中心和半径 [英] DbGeography make circle with center and radius

问题描述

  String selectedLocation = String.Format（POINT（{0} { 1}），lon，lat）。替换（，，。）; 
 DbGeography selectedLocationGeo = DbGeography.FromText（selectedLocation，4326）; 
  

我也有一个半径R。

我想创建一个具有圆点形状的曲线多边形，该圆弧具有从点坐标指定的半径。请注意，我使用DbGeography，而不是DbGeometry。

如何创建CIRCULARSTRING？或者比使用CIRCULARSTRING有更好的方法？

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这样的东西可能吗？

  String polyString = String.Format（CURVEPOLYGON（CIRCULARSTRING（xx yy，xx yy，xx yy，xx yy，xx yy）））; 
 DbGeography polygon = DbGeography.FromText（polyString，4326）; 
  

谢谢。

解决方案

创建一个 DbGeography 通过创建 PointFromText 然后缓冲区指向半径。对于WGS84坐标系，DbGeography半径单位似乎以公里为单位。

  string textPoint = String.Format（POINT（{0} {1}），经度，纬度） 
 DbGeography point = DbGeography.PointFromText（textPoint，DbGeography.DefaultCoordinateSystemId）; // 4326 = [WGS84] 
 DbGeography targetCircle = point.Buffer（radiusKilometers）; 
  

使用 adrian 关于DbGeography.DefaultCoordinateSystemId。

I create a DbGeography-point like this:

String selectedLocation = String.Format("POINT ({0} {1})", lon, lat).Replace(",", ".");
DbGeography selectedLocationGeo = DbGeography.FromText(selectedLocation, 4326);

I also have a radius R.

I want to create a curvepolygon with the shape of a circle with the specified radius from the point-coordinate. Be aware that I am using DbGeography, and not DbGeometry.

How do I create the CIRCULARSTRING? Or is there a better way than using a CIRCULARSTRING?

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Something like this perhaps?

String polyString = String.Format("CURVEPOLYGON(CIRCULARSTRING(xx yy, xx yy, xx yy, xx yy, xx yy))");
DbGeography polygon = DbGeography.FromText(polyString, 4326);

Thanks.

解决方案

Create a DbGeography Circle by creating a PointFromText and then Buffer that point by the radius. For the WGS84 coordinate system the DbGeography radius units appear to be in kilometers.

string textPoint = String.Format("POINT ({0} {1})", longitude, latitude);
DbGeography point = DbGeography.PointFromText(textPoint, DbGeography.DefaultCoordinateSystemId); //4326 = [WGS84]
DbGeography targetCircle = point.Buffer(radiusKilometers);

Edited with info from adrian about DbGeography.DefaultCoordinateSystemId.

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