Extracting Derived Z-coordinate data

Question

I am trying to extract the z coordinate value from the derived attributes, similar to How to re-calculate area, perim, p2a,width and length in QGIS? but I cannot see a dedicated operator for finding the z coordinate like when trying to find area within the field calculator.

I have tried extraction of geometry tools > extract nodes & export/add geometry columns

Yes it only returns Null from the vector layer, after extracting the nodes the Z coordinate is lost and I am only left with X & Y — nashm999, Nov 07 '17 at 12:15
I have a similar problem. To get Z coordinate from polygons you need to tell what is the vertice you want Z. z(point_n($geometry ,1)) The problem while calculating Z coordinate from polygons is that Z returned is an integer. I need Z real, i´ve tryed a lot of other ways inside calculator and keep getting an integer. — Bruno ReZende, Jan 29 '19 at 18:33
This does not really answer the question. If you have a different question, you can ask it by clicking Ask Question. You can also add a bounty to draw more attention to this question once you have enough reputation. - From Review — xunilk, Jan 29 '19 at 18:56

score 6 · Answer 1 · edited Jul 25 '19 at 02:23

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Apparently the z function available in the Geometry section of the field calculator works well with points. I was able to find a solution to a similar problem of that asked by the OP by using z(start_point($geometry)) in the field calculator.

edited Jul 25 '19 at 02:23

tinlyx

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answered Jul 24 '19 at 21:46

Javgs

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score 5 · Accepted Answer · answered Nov 07 '17 at 12:12

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You could try How to „extract“ z-values ? to open the attribute-table, go directly into the field-calculator. Within the geometry-functions you will find z

Just calculate z on the geometry: z ($geometry)

answered Nov 07 '17 at 12:12

whyzar

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Extracting Derived Z-coordinate data

2 Answers2