Whilst working with OGR, I came across the following field used define a geographic dataset:
The spatial dimension (2, 3 or 4 dimensional) of the column.
Whilst I've used 2D and 3D features, are there any examples of datasets in GIS that use the fourth dimension, and do any GIS systems actually handle these?
The 4d with regards to OGR / PostGIS is likely to be used for M-values (M-Aware in ArcGIS) (though I've yet to find this in a tech doc). However the quesion of (real?!) 4d in GIS remains open.