问题描述
在R中-我已将不直的多段线shapefile(表示蜿蜒的州际公路)导入到环境中.我已经阅读了一个.csv文件，其中包含指向环境的点(以十进制表示的纬度/经度).所有这些点都位于多义线上.
In R - I have imported a polyline shapefile that is not straight (represents a winding interstate highway) into the environment. I have read a .csv file that contains points (latitude/longitude in decimal degrees) into the environment. All of those points lie along the polyline.
如果我取了两个随机点，我可以使用大圆距离计算来计算它们之间的乌鸦飞翔"距离.但是需要的是沿着折线的距离.查看参考图片:
If I take two random points I can calculate the "as the crow flies" distance between them using great circle distance calculation. But what is needed is distance traveled along the polyline. See reference image:
https://i.stack.imgur.com/zhorb.png
有人知道R包可以计算沿一条折线的两个纬度/经度点之间的距离吗?
Is anyone aware of an R package that can calculate the distance between two lat/lon points along a polyline?
推荐答案
数据包PBSmapping具有calcLength函数，该函数直接计算折线或多边形的长度(即PolySet).如果您的shapefile采用该格式，则该包也可以导入ESRI shapefile.
Package PBSmapping has a calcLength function which directly calculates the length of a polyline or polygon (in what it terms a PolySet). The package can import ESRI shapefiles as well, if your shapefile is in that format.
简单折线的示例:
line = read.table(text = "X, Y, POS, PID
37.772, -122.214, 1, 1
21.291, -157.821, 2, 1
-18.142, 178.431, 3, 1
-27.467, 153.027, 4, 1", header = TRUE, sep = ",")
library(PBSmapping)
pline = as.PolySet(line, projection = 1)
calcLength(pline)
PID length
1 1 404.8539
plotLines(pline)
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