Hi Paolo,
I've been thinking of this as well and I would love it! I hate ending up
with a huge circle on my screen after performing a quick "look how easy
qgis processing is!" 500 degrees buffer on my data. :)
The problem is that you cannot convert degrees to meters so easily since
they depend on the location on earth. I'm sure you know.
So even for smaller areas, for example my house in the Netherlands,
there would already be a 1 : 1.5 difference between lat:lon. Pretty
hard to tell the buffer function.
On smaller scales, for example a country map of Chile, there would also
be big differences in the distances on the north and south sides of the
country.
So I would say, don't do it! I'm afraid this is the reason for being
stuck with all these map projections in geography.
Still, qgis could improve on this I think:
1. Automatically reproject the data to the appropriate CRS (?), perform
the analysis, and reproject back. UTM could be used for it, hoping all
data is in a single zone.
2. Showing the CRS units in the analysis dialog, maybe even in
red/italic/bold when these are degrees.
I'd vote for option 2 here, since I like to know what happened to my
data. Buffers performed in different (overlapping) CRS's won't be exact
the same.
Regards,
Raymond
Btw, here is a nice example story about this:
https://miamigeographic.com/2014/07/22/into-perspective-miami-world-city-distances/
On 05-03-17 08:15, Paolo Cavallini wrote:
Hi all,
when analyses are done on degrees CRS, often parameters are difficult to
use (e.g. buffer width in degrees is not easy to calculate). The usual
strategy is to convert layers first to a metric CRS.
Would it make sense to always input params as meters, and reproject the
parameters as appropriate? This would be far easier for the user.
All the best.
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