Today I tried QGIS 2.13 (dev-version of the upcoming 2.14) and had a look at the now implemented support for „3D-Features“ (2.5d support). It works well and makes the workflow described some months ago easier.
It looks like QGIS 2.14 will have backend support for „z-values“ – deriving z-values for features can be done with GRASS (v.drape) or maybe you already got a Shapefile, FileGDB (yes, FGDBs are recognized with 2.5d features) etc. and want to calculate z-values (extract them from the data).
I did some tests with different feature-types and data-formats and also compared it with the values derived with ArcGIS.
How to „extract“ z-values ?
The workflow is very similar to ArcGIS – just open the attribute-table of the 2.5d dataset and go directly into the field-calculator. Within the „geometry-functions“ you will find „z“ 🙂
- With point-features (data as SHP) it is easy and works well. Just calculate z on the geometry: z ($geometry)
- I also tried line-features 😉 – in this case you have to be a bit more tricky. But with field-calculator it is no problem to derive the z-values for the start- or endnode. The values are identical to the ArcGIS-calculation.
„Line-Options“ in ArcGIS:
- … and a very nice fact: The OpenFileGDB connector recognizes FileGeodatabases (FileGDB) with 2.5d features and although there is no write-support with the OpenFileGDB connector, it is possible to calculate z-values as Virtual Fields.
Thanks to Anita Graser (aka underdark) for the hint of the already implemented 2.5d support in 2.13dev.