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include index of MultiLineString geometries in nearest-point-on-line #2574

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Merged
mfedderly merged 3 commits into from
Aug 6, 2024
Merged

include index of MultiLineString geometries in nearest-point-on-line #2574

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38e084f
include index of multilinestring geometries in nearest-point-on-line
andrewharvey Jan 31, 2024
1875f39
readme updated
andrewharvey Jan 31, 2024
df86ad3
prefix unused variable with _
andrewharvey Jan 31, 2024
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2 changes: 1 addition & 1 deletion packages/turf-nearest-point-on-line/README.md
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Expand Up @@ -34,7 +34,7 @@ var addToMap = [line, pt, snapped];
snapped.properties['marker-color'] = '#00f';
```

Returns **[Feature][4]<[Point][1]>** closest point on the `line` to `point`. The properties object will contain three values: `index`: closest point was found on nth line part, `dist`: distance between pt and the closest point, `location`: distance along the line between start and the closest point.
Returns **[Feature][4]<[Point][1]>** closest point on the `line` to `point`. The properties object will contain four values: `index`: closest point was found on nth line part, `multiFeatureIndex`: closest point was found on the nth line of the `MultiLineString`, `dist`: distance between pt and the closest point, `location`: distance along the line between start and the closest point.

[1]: https://tools.ietf.org/html/rfc7946#section-3.1.2

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170 changes: 93 additions & 77 deletions packages/turf-nearest-point-on-line/index.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -15,7 +15,7 @@ import { getCoords } from "@turf/invariant";
* @param {Geometry|Feature<Point>|number[]} pt point to snap from
* @param {Object} [options={}] Optional parameters
* @param {string} [options.units='kilometers'] can be degrees, radians, miles, or kilometers
* @returns {Feature<Point>} closest point on the `line` to `point`. The properties object will contain three values: `index`: closest point was found on nth line part, `dist`: distance between pt and the closest point, `location`: distance along the line between start and the closest point.
* @returns {Feature<Point>} closest point on the `line` to `point`. The properties object will contain four values: `index`: closest point was found on nth line part, `multiFeatureIndex`: closest point was found on the nth line of the `MultiLineString`, `dist`: distance between pt and the closest point, `location`: distance along the line between start and the closest point.
* @example
* var line = turf.lineString([
* [-77.031669, 38.878605],
Expand All @@ -42,6 +42,7 @@ function nearestPointOnLine<G extends LineString | MultiLineString>(
{
dist: number;
index: number;
multiFeatureIndex: number;
location: number;
[key: string]: any;
}
Expand All @@ -52,96 +53,111 @@ function nearestPointOnLine<G extends LineString | MultiLineString>(

let closestPt: Feature<
Point,
{ dist: number; index: number; location: number }
{ dist: number; index: number; multiFeatureIndex: number; location: number }
> = point([Infinity, Infinity], {
dist: Infinity,
index: -1,
multiFeatureIndex: -1,
location: -1,
});

let length = 0.0;
flattenEach(lines, function (line: any) {
const coords: any = getCoords(line);
flattenEach(
lines,
function (line: any, _featureIndex: number, multiFeatureIndex: number) {
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@mfedderly mfedderly Aug 5, 2024

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should we add the featureIndex too since we have it?

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@andrewharvey andrewharvey Aug 6, 2024 •
edited
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This method is having an identity crisis, it's called nearestPointOn**Line** (singular) implying it only accepts one line, however the first argument is named lines (plural) implying it accepts multiple lines, the lines argument type is defined to accept Geometry|Feature<LineString|MultiLineString> which implies only a single line Feature is accepted, albeit you can have a MultiLineString geometry within that single Feature, however it may also accept multiple lines through a GeometryCollection type of Geometry.

Checking the implementation it just passes lines through to flattenEach which accepts FeatureCollection | Feature | Geometry thereby giving rise to the featureIndex.

We should decide that either:

  1. the function is to only accept a single line feature and therefore doesn't need to deal with featureIndex or,
  2. the function can accept multiple features and therefore also include the featureIndex in the result.

While officially supporting FeatureCollection sounds like a good idea, it gets complicated when that FeatureCollection contains multiple geometry types, and defining how the method behaves in those situations is messy. On the other hand we already support GeometryCollection which has the same issue. 🤷

I think for now we go ahead and just include the multiFeatureIndex and leave the decision on featureIndex to another discussion/issue/PR.

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@mfedderly mfedderly Aug 6, 2024

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Fair points, thanks for the detailed writeup!

const coords: any = getCoords(line);

for (let i = 0; i < coords.length - 1; i++) {
//start
const start: Feature<Point, { dist: number }> = point(coords[i]);
start.properties.dist = distance(pt, start, options);
//stop
const stop: Feature<Point, { dist: number }> = point(coords[i + 1]);
stop.properties.dist = distance(pt, stop, options);
// sectionLength
const sectionLength = distance(start, stop, options);
//perpendicular
const heightDistance = Math.max(
start.properties.dist,
stop.properties.dist
);
const direction = bearing(start, stop);
const perpendicularPt1 = destination(
pt,
heightDistance,
direction + 90,
options
);
const perpendicularPt2 = destination(
pt,
heightDistance,
direction - 90,
options
);
const intersect = lineIntersects(
lineString([
perpendicularPt1.geometry.coordinates,
perpendicularPt2.geometry.coordinates,
]),
lineString([start.geometry.coordinates, stop.geometry.coordinates])
);
let intersectPt:
| Feature<Point, { dist: number; location: number }>
| undefined;
for (let i = 0; i < coords.length - 1; i++) {
//start
const start: Feature<Point, { dist: number }> = point(coords[i]);
start.properties.dist = distance(pt, start, options);
//stop
const stop: Feature<Point, { dist: number }> = point(coords[i + 1]);
stop.properties.dist = distance(pt, stop, options);
// sectionLength
const sectionLength = distance(start, stop, options);
//perpendicular
const heightDistance = Math.max(
start.properties.dist,
stop.properties.dist
);
const direction = bearing(start, stop);
const perpendicularPt1 = destination(
pt,
heightDistance,
direction + 90,
options
);
const perpendicularPt2 = destination(
pt,
heightDistance,
direction - 90,
options
);
const intersect = lineIntersects(
lineString([
perpendicularPt1.geometry.coordinates,
perpendicularPt2.geometry.coordinates,
]),
lineString([start.geometry.coordinates, stop.geometry.coordinates])
);
let intersectPt:
| Feature<
Point,
{ dist: number; multiFeatureIndex: number; location: number }
>
| undefined;

if (intersect.features.length > 0 && intersect.features[0]) {
intersectPt = {
...intersect.features[0],
properties: {
dist: distance(pt, intersect.features[0], options),
location: length + distance(start, intersect.features[0], options),
},
};
}
if (intersect.features.length > 0 && intersect.features[0]) {
intersectPt = {
...intersect.features[0],
properties: {
dist: distance(pt, intersect.features[0], options),
multiFeatureIndex: multiFeatureIndex,
location:
length + distance(start, intersect.features[0], options),
},
};
}

if (start.properties.dist < closestPt.properties.dist) {
closestPt = {
...start,
properties: { ...start.properties, index: i, location: length },
};
}
if (start.properties.dist < closestPt.properties.dist) {
closestPt = {
...start,
properties: {
...start.properties,
index: i,
multiFeatureIndex: multiFeatureIndex,
location: length,
},
};
}

if (stop.properties.dist < closestPt.properties.dist) {
closestPt = {
...stop,
properties: {
...stop.properties,
index: i + 1,
location: length + sectionLength,
},
};
}
if (stop.properties.dist < closestPt.properties.dist) {
closestPt = {
...stop,
properties: {
...stop.properties,
index: i + 1,
multiFeatureIndex: multiFeatureIndex,
location: length + sectionLength,
},
};
}

if (
intersectPt &&
intersectPt.properties.dist < closestPt.properties.dist
) {
closestPt = {
...intersectPt,
properties: { ...intersectPt.properties, index: i },
};
if (
intersectPt &&
intersectPt.properties.dist < closestPt.properties.dist
) {
closestPt = {
...intersectPt,
properties: { ...intersectPt.properties, index: i },
};
}
// update length
length += sectionLength;
}
// update length
length += sectionLength;
}
});
);

return closestPt;
}
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22 changes: 22 additions & 0 deletions packages/turf-nearest-point-on-line/test.ts
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Expand Up @@ -375,3 +375,25 @@ test("turf-point-on-line -- Geometry Support", (t) => {
);
t.end();
});

test("turf-point-on-line -- multifeature index", (t) => {
const pt = point([4, 30]);
const multiLine = multiLineString([
[
[7, 50],
[8, 50],
[9, 50],
],
[
[17, 30],
[4, 30],
[2, 30],
],
]);
t.equal(
nearestPointOnLine(multiLine.geometry, pt).properties.multiFeatureIndex,
1,
"multiFeatureIndex"
);
t.end();
});
11 changes: 10 additions & 1 deletion ...ges/turf-nearest-point-on-line/test/out/expectedLocation - points behind first point.json
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@@ -1 +1,10 @@
[0, 0, 0, 0, 0, 0, 0, 0]
[
0,
0,
0,
0,
0,
0,
0,
0
]
7 changes: 6 additions & 1 deletion ...turf-nearest-point-on-line/test/out/expectedLocation - points in front of last point.json
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@@ -1 +1,6 @@
[0.362058, 0.362058, 0.362058, 0.362058]
[
0.362058,
0.362058,
0.362058,
0.362058
]
58 changes: 31 additions & 27 deletions packages/turf-nearest-point-on-line/test/out/expectedLocation - points on joints.json
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@@ -1,29 +1,33 @@
[
[0, 0.162908, 0.362058],
[
0,
435.152731,
848.38422,
1506.62747,
1877.71515,
2362.640364,
2951.524644,
3346.548084,
3711.226929
],
[
0,
0.011338,
0.021306,
0.033964,
0.057049,
0.082838,
0.161154,
0.207251,
0.243733,
0.287901,
0.320556,
0.396017,
0.491916
]
[
0,
0.162908,
0.362058
],
[
0,
435.152731,
848.38422,
1506.62747,
1877.71515,
2362.640364,
2951.524644,
3346.548084,
3711.226929
],
[
0,
0.011338,
0.021306,
0.033964,
0.057049,
0.082838,
0.161154,
0.207251,
0.243733,
0.287901,
0.320556,
0.396017,
0.491916
]
]
20 changes: 10 additions & 10 deletions packages/turf-nearest-point-on-line/test/out/expectedLocation - points on top of line.json
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@@ -1,12 +1,12 @@
[
0,
0.030566,
0.061133,
0.091699,
0.122265,
0.152831,
0.183398,
0.213964,
0.24453,
0.275097
0,
0.030566,
0.061133,
0.091699,
0.122265,
0.152831,
0.183398,
0.213964,
0.24453,
0.275097
]
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