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package geo
import (
"math"
"github.com/paulmach/orb"
)
// NewBoundAroundPoint creates a new bound given a center point,
// and a distance from the center point in meters.
func NewBoundAroundPoint(center orb.Point, distance float64) orb.Bound {
radDist := distance / orb.EarthRadius
radLat := deg2rad(center[1])
radLon := deg2rad(center[0])
minLat := radLat - radDist
maxLat := radLat + radDist
var minLon, maxLon float64
if minLat > minLatitude && maxLat < maxLatitude {
deltaLon := math.Asin(math.Sin(radDist) / math.Cos(radLat))
minLon = radLon - deltaLon
if minLon < minLongitude {
minLon += 2 * math.Pi
}
maxLon = radLon + deltaLon
if maxLon > maxLongitude {
maxLon -= 2 * math.Pi
}
} else {
minLat = math.Max(minLat, minLatitude)
maxLat = math.Min(maxLat, maxLatitude)
minLon = minLongitude
maxLon = maxLongitude
}
return orb.Bound{
Min: orb.Point{rad2deg(minLon), rad2deg(minLat)},
Max: orb.Point{rad2deg(maxLon), rad2deg(maxLat)},
}
}
// BoundPad expands the bound in all directions by the given amount of meters.
func BoundPad(b orb.Bound, meters float64) orb.Bound {
dy := meters / 111131.75
dx := dy / math.Cos(deg2rad(b.Max[1]))
dx = math.Max(dx, dy/math.Cos(deg2rad(b.Min[1])))
b.Min[0] -= dx
b.Min[1] -= dy
b.Max[0] += dx
b.Max[1] += dy
b.Min[0] = math.Max(b.Min[0], -180)
b.Min[1] = math.Max(b.Min[1], -90)
b.Max[0] = math.Min(b.Max[0], 180)
b.Max[1] = math.Min(b.Max[1], 90)
return b
}
// BoundHeight returns the approximate height in meters.
func BoundHeight(b orb.Bound) float64 {
return 111131.75 * (b.Max[1] - b.Min[1])
}
// BoundWidth returns the approximate width in meters
// of the center of the bound.
func BoundWidth(b orb.Bound) float64 {
c := (b.Min[1] + b.Max[1]) / 2.0
s1 := orb.Point{b.Min[0], c}
s2 := orb.Point{b.Max[0], c}
return Distance(s1, s2)
}
//MinLatitude is the minimum possible latitude
var minLatitude = deg2rad(-90)
//MaxLatitude is the maxiumum possible latitude
var maxLatitude = deg2rad(90)
//MinLongitude is the minimum possible longitude
var minLongitude = deg2rad(-180)
//MaxLongitude is the maxiumum possible longitude
var maxLongitude = deg2rad(180)
func deg2rad(d float64) float64 {
return d * math.Pi / 180.0
}
func rad2deg(r float64) float64 {
return 180.0 * r / math.Pi
}
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