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I want to give my user the ability to click on the map and give him a dynamic circle drawing tool which also reads out the radius measurement. That way the user can see how big the circle he creates is.

For example, something like this :

enter image description here

Any idea how I can add such a thing to OpenLayers?

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  • 2
    This does not look like a duplicate to me because I can see no mention of the "persist measure of the radius" requirement in the other Question.
    – PolyGeo
    Jan 23, 2014 at 7:42
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    @PolyGeo is correct - I want to show the radius while the user change the drawn circle size
    – Alophind
    Jan 23, 2014 at 8:42
  • Why not provide a text input for the user to directly specify the radius instead.
    – nagytech
    Jun 27, 2015 at 23:31

1 Answer 1

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I'd try this way:

  • create a separate layer just for the radii,
  • after each feature creation event on circle layer, construct a LINESTRING with two points: the center of the circle as start point and the easternmost vertex as end point, and calculate its length,
    • add this temporary feature to radii layer and label it with its length.

EDIT: I created a sample jsFiddle for this: http://jsfiddle.net/5TQHK/24/. Beware that if you use EPSG:900913, the calculated length will be too distorted to be useful. Use a local coordinate system or geodesic calculations to get meaningful length.

(I know that real circles don't have vertices, but in most GIS systems they do :) )

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  • Very nice , Is there a way to show the radius size while the circle being draw ? like in this example : jorix.github.io/OL-DynamicMeasure/examples/measure-dynamic.html
    – Alophind
    Jan 23, 2014 at 13:58
  • Yes, this should be possible as well. To do this you will need to capture the circle geometry at every move. Refer to OpenLayers source code, lib/OpenLayers/Handler/RegularPolygon.js to see how the circle geometry is being constructed and get some idea. Jan 23, 2014 at 21:11

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