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Fix IndexedCoordinate.distance to be distance along the line #14

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Merged
nighthawk merged 1 commit into from
Jun 29, 2023
Merged

Fix IndexedCoordinate.distance to be distance along the line #14

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46 changes: 29 additions & 17 deletions Sources/GeoJSONKitTurf/ClosestCoordinate.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -17,9 +17,11 @@ extension GeoJSON.LineString {
public struct IndexedCoordinate {
/// The coordinate
public let coordinate: Array<GeoJSON.Position>.Element

/// The index of the coordinate
public let index: Array<GeoJSON.Position>.Index
/// The coordinate’s distance from the start of the polyline

/// The coordinate’s distance along the polyline from the start of the polyline
public let distance: GeoJSON.Distance
}

Expand All @@ -36,37 +38,47 @@ extension GeoJSON.LineString.IndexedCoordinate {
}

var closestCoordinate: GeoJSON.LineString.IndexedCoordinate?
var closestDistance: GeoJSON.Distance?
var closestDistance: GeoJSON.Distance = .greatestFiniteMagnitude
var cumulativeDistance: GeoJSON.Distance = 0

for index in 0..<coordinates.count - 1 {
let segment = (coordinates[index], coordinates[index + 1])
let segmentDistance = segment.0.distance(to: segment.1)
let distances = (coordinate.distance(to: segment.0), coordinate.distance(to: segment.1))

let maxDistance = max(distances.0, distances.1)
let direction = segment.0.direction(to: segment.1)
let perpendicularPoint1 = coordinate.coordinate(at: maxDistance, facing: direction + 90)
let perpendicularPoint2 = coordinate.coordinate(at: maxDistance, facing: direction - 90)
let intersectionPoint = intersection((perpendicularPoint1, perpendicularPoint2), segment)
let intersectionDistance: GeoJSON.Distance? = intersectionPoint != nil ? coordinate.distance(to: intersectionPoint!) : nil


if distances.0 < closestDistance ?? .greatestFiniteMagnitude {
closestCoordinate = GeoJSON.LineString.IndexedCoordinate(coordinate: segment.0,
index: index,
distance: startCoordinate.distance(to: segment.0))

if distances.0 < closestDistance {
closestCoordinate = GeoJSON.LineString.IndexedCoordinate(
coordinate: segment.0,
index: index,
distance: cumulativeDistance)
closestDistance = distances.0
}
if distances.1 < closestDistance ?? .greatestFiniteMagnitude {
closestCoordinate = GeoJSON.LineString.IndexedCoordinate(coordinate: segment.1,
index: index + 1,
distance: startCoordinate.distance(to: segment.1))
if distances.1 < closestDistance {
closestCoordinate = GeoJSON.LineString.IndexedCoordinate(
coordinate: segment.1,
index: index + 1,
distance: cumulativeDistance + segmentDistance)
closestDistance = distances.1
}
if intersectionDistance != nil && intersectionDistance! < closestDistance ?? .greatestFiniteMagnitude {
closestCoordinate = GeoJSON.LineString.IndexedCoordinate(coordinate: intersectionPoint!,
index: index,
distance: startCoordinate.distance(to: intersectionPoint!))
closestDistance = intersectionDistance!
if let intersectionPoint = intersection((perpendicularPoint1, perpendicularPoint2), segment) {
let intersectionDistance = coordinate.distance(to: intersectionPoint)
if intersectionDistance < closestDistance {
closestCoordinate = GeoJSON.LineString.IndexedCoordinate(
coordinate: intersectionPoint,
index: index,
distance: cumulativeDistance + intersectionDistance)
closestDistance = intersectionDistance
}
}

cumulativeDistance += segmentDistance
}

return closestCoordinate
Expand Down
10 changes: 6 additions & 4 deletions Sources/GeoJSONKitTurf/Turf+LineString.swift
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Expand Up @@ -35,15 +35,15 @@ extension GeoJSON.LineString {
*/
public func trimmed(from startDistance: GeoJSON.Distance, to stopDistance: GeoJSON.Distance) -> GeoJSON.LineString? {
// The method is porting from https://github.com/Turfjs/turf/blob/5375941072b90d489389db22b43bfe809d5e451e/packages/turf-line-slice-along/index.js
guard startDistance >= 0.0 && stopDistance >= startDistance else { return nil }
guard startDistance >= 0, stopDistance >= startDistance else { return nil }
let positions = self.coordinates
var traveled: GeoJSON.Distance = 0
var slice = [GeoJSON.Position]()

for i in 0..<positions.endIndex {
if startDistance >= traveled && i == positions.endIndex - 1 {
if startDistance >= traveled, i == positions.endIndex - 1 {
break
} else if traveled > startDistance && slice.isEmpty {
} else if traveled > startDistance, slice.isEmpty {
let overshoot = startDistance - traveled
if overshoot == 0.0 {
slice.append(positions[i])
Expand Down Expand Up @@ -77,7 +77,9 @@ extension GeoJSON.LineString {
traveled += positions[i].distance(to: positions[i + 1])
}

if traveled < startDistance { return nil }
if traveled < startDistance {
return nil
}

if let last = positions.last {
return GeoJSON.LineString(positions: [last, last])
Expand Down