I am using QGIS 3.6 and trying to calculate coordinates (lat&long) from a point given the distance. I have the lat&long for reference point and have the distance from the reference point.

Table 1

Points A, B, and C are reference locations of a road

Table 2

X, Y, and Z are building within a distance from A toward point B How can I get the lat and long for X, Y, Z?

  • Don't you need a direction as well? – alphabetasoup Jun 25 '19 at 21:30
  • Can I get the direction from point A to B? Cause these buildings are on A to B line – Hoda Rezaei Jun 25 '19 at 21:45
  • Oh, so the buildings are on the line that starts at A, goes to B, then C? – alphabetasoup Jun 25 '19 at 22:12
  1. Use the points A, B and C to create a line. There are many ways to do this, including:

    • use the points to path tool, or
    • use the geometry by expression tool, or
    • create a line with three vertices, and edit the vertex coordinates using the vertex editor
  2. Use the interpolate point on line tool to create a point at each specified distance. To create multiple points, there are two options. Choose the one that seems most convenient for your dataset.

    • Method one: Run the tool once for each point. This method creates a separate layer for each point. You can merge them into a single layer using the merge vector layers tool.
    • Method two: Make a duplicate line for every point you want to create (select the line, copy and paste). Add an attribute field called distance. Enter the point distances in this field.

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    Use the distance field for the distance value.

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  3. Get the lat/long of those points by

    • clicking on each point with the Identify tool, or
    • use the add geometry attributes tool to add lat/long to the attribute table
  • You can also use interpolate point on line for step 2 – strythe Jun 25 '19 at 23:52
  • 1
    @strythe, thank you for the suggestion. I thought there was a tool that did the same as points along geometry but allowed a data-defined override for the distance value. – csk Jun 27 '19 at 17:04
  • I was hoping there'd be a tool for this too, one which takes a field of distances and a line geometry.I had to write a script to interpolate multiple points without having to duplicate the line. – strythe Jun 28 '19 at 0:11

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