Default Z value handling - part 2 - use Nan in QGIS and defautl value in providers

[haubourg]

[haubourg]

Already discussed before when implementing default z in QGIS 3. Now the idea is to handle real Nan values in QGIS, but map them to default values in providers because NULL z is never supported by providers.

[ponceta]

@haubourg does this has been assigned to @m-kuhn?

[haubourg]

To me assigning means we have prioritized the work and we have the budget available, which is not the case yet. So In my mind it was for 2018 plans.

[ponceta]

Ok, thanks for the details.