Path is just a straight line defined by coordinates of the beginning and end of it.

My coordinates are simply longitude and latitude of three points:

  • start of the path
  • end of the path
  • my point (for which I want to check if it's near a given path)

Given that my paths are in the mountains I think the best would be to get a distance in the idealized 3D space.

I expect my point to be up to 25-50 meters away from the path.

closed as unclear what you're asking by Paul, Mapperz Jan 25 '16 at 22:19

Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

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    what software do you plan on using? what are you looking to gather - distance from path, etc? – MDHald Jan 25 '16 at 20:38
  • I'm not using any software at this moment - I'm about to write my own software. Yes - distance from the path would be great. I'm not sure if this is important or no - but my paths are in the mountains (so start and end are always at different altitudes) - think ski/snowboard lifts. – Inez Jan 25 '16 at 20:39
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    What programming language? What GPS software? What format is your data in? You are missing a lot of details that would be helpful. Please take the community tour and see the help page on asking questions As it stands, your question is too vague. – MaryBeth Jan 25 '16 at 20:47
  • I have coordinates as longitude and latitude - so three coordinates, start of the line, end of the line, and my point. Language does not matter - I'm looking for a algorithm - which I will be able to convert to any language. – Inez Jan 25 '16 at 20:49
  • Do you want distance on a 2D plane, or distance in idealized 3D space (without a terrain model) or distance along the real topographic surface? What lengths do you plan to calculate (100km or 50m)? – til_b Jan 25 '16 at 20:53

You may want to review the Paul Ramsey PostGIS Gotchas You Tube Video. The video link starts at the distance discussion. There are pitfalls with every coordinate system. The thing that caught my eye along time ago when I saw a similar video is that a GPS point may not be under the line that your two other GPS points draw.

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