[gdal-dev] Support for measures

[Ari Jolma]

28.01.2016, 00:05, Even Rouault kirjoitti:

Thanks for the pointer to the geometry codes in SF Common Architecture, 
somehow I overlooked it.

> my point with adding the new capabilities was that drivers that 
> wouldn't advertize the M capabilities would never see a M or ZM 
> geometry / geometry type passed. See what the (non-virtual) methods 
> OGRLayer::SetFeature(),CreateFeature() and GDALDataset::CreateLayer() 
> do for curve geometries. Similar things could be done for M. 

Hm. For example shape driver raises an error if the geometry type is not 
supported. I don't know what scenario would lead to that.

Assume that the user has data in GDAL with measures. She decides to save 
that using a driver, which does not support measures. The impact is that 
the measures are stripped out, which is ok if the data is discarded 
immediately after that but not if she wants to still do something with 
the measures. I'm not sure if documenting the side-effect is enough. 
However, the convert to non linear geometries is already there and this 
would follow that pattern. I guess this is a part of the bigger 
discussion whether we consider GDAL as a data storage for interactive 
tools for example or as a data processing library.

Ari