I have 2 layers (Point_Orien_Vert - red points and Point_Centroides - green points), both are Point Geometry.

Attribute tables of both layers

I need first to check if the distance between one feature in Point_Orien_Vert and one feature in Point_Centroide is smaller than 180 m.

The code below shows how to calculate this distance and it works inside a IF statement.

       'POINT_Centroides', "fid"
  , @geometry

If the result is true, I need to calculate in Point_Orien_Vert layer the difference between the value stored in "Dip_Direct" and the value "Azimute".

Note that a feature from Point_Centroide will be checked more than an once time from points in Point_Orien_vert because the distance.

I do not know how to write this second code using self-referencing geometry to do this operation.

1 Answer 1

  • The closest point of a point geometry, is the point itself. Also, the distance between geometries, is the distance between their closest points.

  • "fid" attribute may or may not have the id of the feature as its value. If you delete the feature where "fid" = 1, the second feature "fid" value remains as 2, but its new id is 1.

  • Anyways, you don't need its id nor its "fid" value, you need the feature itself. Use the @feature expression in the overlay_nearest function.

  • Don't convert the array to string, get its first item. Even if you were getting the id, this is a number not a string.

  • Store the feature in a variable for later use in the if clause.

with_variable( 'closestfeature',
  expression:=@feature)[0], --slice index 0 to get the first array item
 distance(@geometry, geometry(@closestfeature)) < 180, --condition
 "Dip_Direct" - attribute(@closestfeature, 'Azimute'), --expression for True
 NULL) --expression for False
  • 1
    +1 - A bit shorter: instead of if multiply the condition's result (0 or 1) with the difference of Dip_Direct - Azimute like this: (distance (geometry (@closestfeature), $geometry) < 180) * (Dip_Direct - attribute (@closestfeature, 'Azimute'))
    – Babel
    Nov 8, 2023 at 7:17
  • @Gabriel De Luca thank you very much to help me with this solution and to teach me a bit more about Field Calculator. It works perfectly for my purpose.
    – Mauro_F
    Nov 10, 2023 at 14:09
  • @Babel thank you very much too because you improve the solution and it fits perfectly. Thanks to teach me more about Field Calculator.
    – Mauro_F
    Nov 10, 2023 at 14:12

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