用RGeo和Geojson计算面积

{
  "type": "Feature",
  "geometry": {
    "type": "Polygon",
    "coordinates": [
      [
        [100.0, 0.0],
        [101.0, 0.0],
        [101.0, 1.0],
        [100.0, 1.0],
        [100.0, 0.0]
      ]
    ]
  },
  "properties": {
    "name": "Example Polygon"
  }
}

require 'rgeo'
require 'rgeo-geojson'

# 解析 GeoJSON 数据
geojson = <<-JSON
{
  "type": "Feature",
  "geometry": {
    "type": "Polygon",
    "coordinates": [
      [
        [100.0, 0.0],
        [101.0, 0.0],
        [101.0, 1.0],
        [100.0, 1.0],
        [100.0, 0.0]
      ]
    ]
  },
  "properties": {
    "name": "Example Polygon"
  }
}
JSON

feature = RGeo::GeoJSON.decode(geojson)

# 计算面积
if feature.geometry.is_a?(RGeo::Geographic::Polygon)
  area = feature.geometry.area
  puts "The area of the polygon is: #{area} square meters"
else
  puts "The geometry is not a polygon."
end