R sp:Polygon的面积单位 [英] R sp: unit of area of Polygon

问题描述

我用R读入了一个shape文件，用sp包分析了油田的多边形(WGS84的经纬度)及其各自的区域.不幸的是我不知道面积输出的单位.例如.面积输出平均为 0.85 个单位(最大 4.34 个)，这可能不是以平方公里为单位，因为这对于油田来说太小了.

I use R to read in a shape file to analyse with the sp package polygons of oilfields (longitude-latitude with WGS84) and their respective areas. Unfortunately I do not know the unit of the area output. E.g. the area output is on average 0.85 units (max 4.34) which probably is not in square kilometers since this would be much too small for oilfields.

有谁知道sp包中Polygons的面积输出单位是多少?非常感谢！

Does anyone know the unit of the area output of Polygons in the sp package? Many thanks!

推荐答案

要在纬度坐标系中正确计算多边形的面积，最好使用spTransform"将它们转换为公制等面积投影预先.或者，您可以使用包 geosphere 允许做

To get a correct area computation for a polygon in lat-lon coordinates, it would be better to convert them to a metric equal-area projection using "spTransform" beforehand. Alternatively, you could use package geosphere which allows to do

"地理应用的球面三角学.即计算角度(经度/纬度)的距离和相关测量位置"

"Spherical trigonometry for geographic applications. That is, compute distances and re- lated measures for angular (longitude/latitude) locations"

例如:

require(geosphere)
areaPolygon(mypoly)

(mypoly 是一个 spatialPolygons 对象)将以平方公里为单位给出它的面积.

(with mypoly being a spatialPolygons object) will give you its area in square kilometers.

HTH.

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