44 lines
916 B
Go
44 lines
916 B
Go
package geo
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import (
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"math"
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)
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const (
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DistLimit float64 = 5000
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ScopeDistLimit float64 = 50
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DefaultDist float64 = 2
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)
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// Deg returns the approximate distance in decimal degrees,
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// see https://en.wikipedia.org/wiki/Decimal_degrees.
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func Deg(km float64) float64 {
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return 0.009009009 * km
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}
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// DegToRad converts a value from degrees to radians.
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func DegToRad(d float64) float64 {
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return d * math.Pi / 180
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}
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// Km returns the shortest path between two positions in km.
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func Km(p, q Position) (km float64) {
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if p.Lat == q.Lat && p.Lng == q.Lng {
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return 0.0
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}
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lat1 := DegToRad(p.Lat)
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lng1 := DegToRad(p.Lng)
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lat2 := DegToRad(q.Lat)
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lng2 := DegToRad(q.Lng)
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diffLat := lat2 - lat1
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diffLng := lng2 - lng1
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a := math.Pow(math.Sin(diffLat/2), 2) + math.Cos(lat1)*math.Cos(lat2)*
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math.Pow(math.Sin(diffLng/2), 2)
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c := 2 * math.Atan2(math.Sqrt(a), math.Sqrt(1-a))
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return c * EarthRadiusKm
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}
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