[GRASS-dev] wxGUI: align to resolution by default

Blumentrath, Stefan Stefan.Blumentrath at nina.no
Thu Jan 5 02:42:30 PST 2017


Actually, I would have no strong opinions about this. However, I am a bit confused...

Cause I almost never use the a-flag.

In fact I use the a-flag only when I want to interpolate e.g. LiDAR point clouds to a new raster with a nice resolution. In all other cases I use the align option, when I want my data to match with the resolution of an existing raster (most of the time a terrain model). 

So, when I want to grab the extend from a vector map but want to keep the pixels from my DEM I do:
g.region -p vector=vect_map align=rast_map

For a reported Processing bug in QGIS I even suggested to drop the usage of the a-flag (which Processing used as a default): https://hub.qgis.org/issues/14582
So now I am a bit unsure if my suggestion for Processing bug #14582 was correct... I still think dropping the a-flag was correct for the processing use case ...

Finally, I had a look into the g.region manual and was surprised to see that there is neither an example using the a-flag nor the align option. Would be probably worth adding this. If you agree I can come up with suggestions...

And probably also the description of the a flag could be slightly reworded into e.g.:
"Adjust region extent to be a multiple of the resolution (default = align to bounds, works only for 2D resolution)" (which was: "Align region to resolution (default = align to bounds, works only for 2D resolution)").


-----Original Message-----
From: grass-dev [mailto:grass-dev-bounces at lists.osgeo.org] On Behalf Of Martin Landa
Sent: torsdag 5. januar 2017 11.05
To: Moritz Lennert <mlennert at club.worldonline.be>
Cc: GRASS developers list <grass-dev at lists.osgeo.org>
Subject: Re: [GRASS-dev] wxGUI: align to resolution by default


2017-01-05 8:30 GMT+01:00 Moritz Lennert <mlennert at club.worldonline.be>:
>>What do you think? Ma
> See the arguments at
> https://trac.osgeo.org/grass/ticket/1745

hm, I found two reasons there:

1) Using '-a' breaks that by rounding - not surprissing
2) by default GRASS should try to do the least-damaging thing

Well I used -a flag everytime when setting up region based on vector and raster data. I still think that it could be default in wxGUI. In 99% you want to preserve resolution. Ma

Martin Landa
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