Turf: Find nearest position on a linestring

[avinmathew]

Is there a way to determine the nearest position on a linestring to a given point? I'm looking to snap a point to its closest position on a line.

nearestPointOnLine returns the nearest vertex while pointToLineDistance returns the distance to the nearest position, but not the actual coordinate.

[rowanwins]

Hi @avinmathew

nearestPointOnLine doesn't always returns a vertex, I think the example on the website just happens to do so. Have you tried using it yet or were you just looking at the example?

Thanks,

[avinmathew]

You're correct, it does return a point in the geometry.coordinates of the return value. I got caught up in the properties section that I missed it.

Thanks.

[wishinghand]

I'm having a similar issue- I'm only getting results that return the nearest vertex, not the nearest point on a line.

I basically copied the example:

let line = turf.lineString(outline)
let pt = turf.point([event.layer._latlng.lat, event.layer._latlng.lng])
let snapped = turf.nearestPointOnLine(line, pt)

and snapped returns one of the coordinates in outline

outline is:

[
  [37.33292431975684, -121.8855079589412],
  [37.332557495875015, -121.88629116397354],
  [37.332199201052006, -121.88605512958024],
  [37.33256602668332, -121.88521828036758]
]

The lat/lng for the point is:

[ 37.330305508499606,  -121.8795132637024 ]

and then I use snapped.geometry.coordinates, as it's the only pair of coordinates being returned. Every time it turns out to be one of the coordinates from outline.

[wishinghand]

Something I noticed when I put my numbers into a fiddle for demonstrating this function is that it's waaaay off.

Compare a jsfiddle with real numbers that we'd use here: https://jsfiddle.net/wishinghand/jeb1o72p/2/

and one with numbers I had to tweak in order for it not to be in Antarctica: https://jsfiddle.net/wishinghand/mjtz6yLc/10/

[wishinghand]

Oh hell, I just figured it out. Turf uses Long/Lat, and Leaflet uses Lat/Long.