I am trying to manually add one constant Z-variable (e.g. 200meters) across an entire Vector Layer in Qgis so that I may eventually use the Interpolation plugin to generate a Tin.
I have not been able to find any information on how to do this on the website. Is this possible?
Best Answer
As of version 2.10, QGIS supports Z and M values. (See corresponding changelog entry)
In QGIS 3.4, there is a Processing tool called Set Z value to add a constant Z value and there is Drape to add Z from a raster.
Old answer
Just add another attribute to the vector layer's attribute table and fill it with the value using Field Calculator. For help with the field calculator, please check the docs: http://docs.qgis.org/2.2/en/docs/user_manual/working_with_vector/field_calculator.html
Note that QGIS does not support 3D geometries so you have to store your z value in the attribute table.