Google Maps API - 沿路线的中点 [英] Google Maps API - Midpoint along route
问题描述
我一直在玩Google Maps / Google方向API。有没有人对我如何能够沿着路线而不是地理中点找到中点提出了一些看法。
理想情况下，我想找到这个中点的经纬值。
有什么想法？我有点难过，希望我能够找到一个建议，而不会疯狂地尝试自己找到答案。
最简单的方法是，您可以先：
1 ）使用GMSGeometryDistance计算路径的总距离，通过GMSGeometryDistance函数计算每两个后续点之间的距离，然后总和所有距离。2）然后再次计算，并在每一步中加总。当总和大约是总距离的一半时，那么你处于中间点。
示例代码如下：
pre $ func findTotalDistanceOfPath（path：GMSPath） - > Double {
let numberOfCoords = path.count（）
var totalDistance = 0.0
如果numberOfCoords> 1 {
var index = 0 as UInt
while index< numberOfCoords {
//1.1 cal下一个距离
var currentCoord = path.coordinateAtIndex（index）
var nextCoord = path.coordinateAtIndex（index + 1）
var newDistance = GMSGeometryDistance（currentCoord，nextCoord）
totalDistance = totalDistance + newDistance
index = index + 1
$ b return totalDistance
$ b func findMiddlePointInPath（path：GMSPath，totalDistance distance：Double） - > CLLocationCoordinate2D？ {
let numberOfCoords = path.count（）
let halfDistance = distance / 2
let threadhold = 10 // 10 meters
var midDistance = 0.0
如果numberOfCoords> 1 {
var index = 0 as UInt
while index< numberOfCoords {
//1.1 cal下一个距离
var currentCoord = path.coordinateAtIndex（index）
var nextCoord = path.coordinateAtIndex（index + 1）
var newDistance = GMSGeometryDistance（currentCoord，nextCoord）
midDistance = midDistance + newDistance
if fabs（midDistance - halfDistance）< threadhold {//找到路线中的中点
return nextCoord
}
index = index + 1
}
}
return nil //如果我们因为某些原因无法在路径中找到中间点，则返回nil
}
还有更多优化功能。我在此处在Swift中写了一个详细的答案
I've been playing around with the Google Maps/Google directions API. Does anyone have an inkling on how I might be able to find the mid-point along a route, not the geographic midpoint.
Ideally I'd like to find the lat and long values of this midpoint.
Any thoughts? I'm a bit stumped and hoping I may be able to find a suggestion without going crazy trying to find the answer myself.
An easiest way is that you can first:
1) Calculate total distance of the path using GMSGeometryDistance, by calculating the distance between every two subsequent points by GMSGeometryDistance function, then summing all the distance.
2) Then you calculate again, and summing in each step. When the sum is about half of the total distance, then you are at the middle point. Sample code is as following:
func findTotalDistanceOfPath(path: GMSPath) -> Double {
let numberOfCoords = path.count()
var totalDistance = 0.0
if numberOfCoords > 1 {
var index = 0 as UInt
while index < numberOfCoords{
//1.1 cal the next distance
var currentCoord = path.coordinateAtIndex(index)
var nextCoord = path.coordinateAtIndex(index + 1)
var newDistance = GMSGeometryDistance(currentCoord, nextCoord)
totalDistance = totalDistance + newDistance
index = index + 1
}
}
return totalDistance
}
func findMiddlePointInPath(path: GMSPath ,totalDistance distance:Double) -> CLLocationCoordinate2D? {
let numberOfCoords = path.count()
let halfDistance = distance/2
let threadhold = 10 //10 meters
var midDistance = 0.0
if numberOfCoords > 1 {
var index = 0 as UInt
while index < numberOfCoords{
//1.1 cal the next distance
var currentCoord = path.coordinateAtIndex(index)
var nextCoord = path.coordinateAtIndex(index + 1)
var newDistance = GMSGeometryDistance(currentCoord, nextCoord)
midDistance = midDistance + newDistance
if fabs(midDistance - halfDistance) < threadhold { //Found the middle point in route
return nextCoord
}
index = index + 1
}
}
return nil //Return nil if we cannot find middle point in path for some reason
}
There is more to optimize the function. I wrote a detail answer in Swift in here
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