[Qgis-developer] Meaning of "Canvas Units" in project properties?!?

[Giovanni Manghi]

> The thing is, I'm not convinced the area is wrong... it's just that
> QGIS' handling of units with OTF on/off ellipsoid ON/OFF is extremely
> confusing (ie, I don't even fully understand it).

My understanding, at least until http://hub.qgis.org/issues/12057 , is
that the confusing bit is that sometimes areas measured on an
ellipsoid are smaller than the same ones measured on a plane, this
because not all projections are conservative for areas. Differences
are relatively small, of course if the area measured with OTF on
differs of several magnitudes then there is probably something wrong
(but do not seems the case anymore).

There is also the issue with measurements being always in m for
projections in feet, this I can confirm after testing quickly (on
master) the dataset of http://hub.qgis.org/issues/13209 (but
transforming the result from square meters to acres give the right
results).

cheers!

-- G --