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Convert latitude/longitude pair with radius in meters to 16 sided polygon useful in GIS. Useful for converting a Google maps drawing manager circle into a polygon for storage in a GIS system. Implemented as a class method.
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def self.circle_path(center, radius, complete_path = false) | |
# For increased accuracy, if your data is in a localized area, add the elevation in meters to r_e below: | |
r_e = 6378137.0 | |
@@d2r ||= Math::PI/180 | |
@@multipliers ||= begin | |
segments = 16 | |
dRad = 2*Math::PI/segments | |
(segments + (complete_path ? 1 : 0)).times.map do |i| | |
rads = dRad*i | |
y = Math.sin(rads) | |
x = Math.cos(rads) | |
[y.abs < 0.01 ? 0.0 : y, x.abs < 0.01 ? 0.0 : x] | |
end | |
end | |
centerLat = center.first | |
centerLng = center.last | |
dLat = radius/(r_e*@@d2r) | |
dLng = radius/(r_e*Math.cos(@@d2r*centerLat)*@@d2r) | |
@@multipliers.map {|m| [centerLat + m[0]*dLat, centerLng + m[1]*dLng]} | |
end |
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