topic Re: Polyline - Nearest point in ArcGIS API for Silverlight Questions

Polyline - Nearest point

PaulHedlund — Tue, 21 Jun 2011 17:41:31 GMT

How do I find the location on a polyline that is closest to another point on the map. For a visual of what I am looking for, in the attached PolylinePoint.png I want to obtain the yellow "Nearest Point' location.

The geometry task 'DistanceAsync' gets the closest distance between a polyline and point. However, I am looking for that 'Nearest Point' location.

Re: Polyline - Nearest point

wangzhifang — Thu, 23 Jun 2011 01:06:20 GMT

This can be done easily by client side.
Just use dist=Math.Square(a*a+b*b) to calculate every distance between your point and each point on the polyline, then you get the nearest point on the polyline.

Re: Polyline - Nearest point

PaulHedlund — Thu, 23 Jun 2011 01:47:03 GMT

The problem is I am looking for the nearest location on the polyline. The location may not contain a vertex. (see attached visual)

Looping through each vertice and using your forumla would give me the distance from each vertice. But, that is not what I am looking for.

The 'DistanceAsync' task gives me the distance, but for some reason I can't get the polyline nearest location. I would think the value for this would be exposed somewhere.

Re: Polyline - Nearest point

Sravan_KumarUddarraju — Fri, 09 Sep 2011 18:35:27 GMT

I am looking for the samething. I need to find nearest point on the segment.
Were you able to find the solution for this?

Srav

Re: Polyline - Nearest point

SimoLukic — Sun, 11 Sep 2011 17:23:28 GMT

Maybe convert the polyline into a List of Points.
If you have a line between x1 and x5, cut it in pieces and check for distence with x2,x3,x4.

Re: Polyline - Nearest point

DominiqueBroux — Mon, 12 Sep 2011 10:37:22 GMT

If the segment is a straight line (i.e. not an arc, ellipse, ...), it looks easy:
    - project the point on the line,
    - if the projected point is on the segment => it's the shortest distance
    - if not on the segment, thye shortest distance is given by the closest vertex.

Re: Polyline - Nearest point

CostasKotzabassis — Mon, 09 Dec 2013 17:36:40 GMT

Hello Dominique,
I found your response intriguing, but I cannot quite follow.
How do you project a point to a line segment using Silverlight API 3.1?

Re: Polyline - Nearest point

DominiqueBroux — Tue, 10 Dec 2013 05:40:45 GMT

Hello Dominique,
I found your response intriguing, but I cannot quite follow.
How do you project a point to a line segment using Silverlight API 3.1?

I put together a Geometry Projection sample.