87 lines
1.9 KiB
Ruby
87 lines
1.9 KiB
Ruby
class GeojsonService
|
|
def self.to_json_polygon_for_cadastre(coordinates)
|
|
polygon = {
|
|
geom: {
|
|
type: "Feature",
|
|
geometry: {
|
|
type: "Polygon",
|
|
coordinates: [
|
|
coordinates
|
|
]
|
|
}
|
|
}
|
|
}
|
|
|
|
polygon.to_json
|
|
end
|
|
|
|
# The following code is ported from turfjs
|
|
# https://github.com/Turfjs/turf/blob/master/packages/turf-area/index.ts
|
|
|
|
EQUATORIAL_RADIUS = 6378137
|
|
|
|
def self.area(geojson)
|
|
calculate_area(geojson)
|
|
end
|
|
|
|
def self.calculate_area(geom)
|
|
total = 0
|
|
case geom[:type]
|
|
when 'Polygon'
|
|
polygon_area(geom[:coordinates]);
|
|
when 'MultiPolygon'
|
|
geom[:coordinates].each do |coordinates|
|
|
total += polygon_area(coordinates)
|
|
end
|
|
total
|
|
else
|
|
total
|
|
end
|
|
end
|
|
|
|
def self.polygon_area(coordinates)
|
|
total = 0
|
|
if coordinates.present?
|
|
coordinates = coordinates.dup
|
|
total += ring_area(coordinates.shift).abs
|
|
coordinates.each do |coordinates|
|
|
total -= ring_area(coordinates).abs
|
|
end
|
|
end
|
|
total
|
|
end
|
|
|
|
def self.ring_area(coordinates)
|
|
total = 0
|
|
coords_length = coordinates.size
|
|
|
|
if coords_length > 2
|
|
coords_length.times do |i|
|
|
if i == coords_length - 2 # i = N-2
|
|
lower_index = coords_length - 2
|
|
middle_index = coords_length - 1
|
|
upper_index = 0
|
|
elsif i == coords_length - 1 # i = N-1
|
|
lower_index = coords_length - 1
|
|
middle_index = 0
|
|
upper_index = 1
|
|
else # i = 0 to N-3
|
|
lower_index = i
|
|
middle_index = i + 1
|
|
upper_index = i + 2
|
|
end
|
|
p1 = coordinates[lower_index]
|
|
p2 = coordinates[middle_index]
|
|
p3 = coordinates[upper_index]
|
|
total += (rad(p3[0]) - rad(p1[0])) * Math.sin(rad(p2[1]))
|
|
end
|
|
total = total * EQUATORIAL_RADIUS * EQUATORIAL_RADIUS / 2
|
|
end
|
|
|
|
total
|
|
end
|
|
|
|
def self.rad(num)
|
|
num * Math::PI / 180
|
|
end
|
|
end
|