55 lines
1.0 KiB
Go
55 lines
1.0 KiB
Go
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package geoutils
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import (
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"math"
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"github.com/paulmach/orb"
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"github.com/paulmach/orb/geo"
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"github.com/rs/zerolog/log"
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)
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func DistanceFromLineString(point orb.Point, lineString orb.LineString) (distance float64, closestIndex int) {
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minDistance := math.Inf(1)
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closest := -1
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for i := 0; i < len(lineString)-1; i++ {
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a := lineString[i]
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b := lineString[i+1]
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pointOnSegment := projectToSegment(point, a, b)
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dist := geo.Distance(point, pointOnSegment)
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if dist < minDistance {
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minDistance = dist
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closest = i
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}
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}
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log.Debug().
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Float64("min distance", minDistance).
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Int("index", closest).
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Any("point", point).
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Any("linestring", lineString).
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Msg("minimum distance to polyline")
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return minDistance, closest
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}
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func projectToSegment(point, a, b orb.Point) orb.Point {
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x := a[0]
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y := a[1]
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dx := b[0] - x
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dy := b[1] - y
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if dx != 0 || dy != 0 {
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t := ((point[0]-x)*dx + (point[1]-y)*dy) / (dx*dx + dy*dy)
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if t > 1 {
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x = b[0]
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y = b[1]
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} else if t > 0 {
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x += dx * t
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y += dy * t
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}
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}
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return orb.Point{x, y}
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}
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