[GRASS-user] v.to.rast

[Blumentrath, Stefan]

Hi Patrick,

From my experience r.in.xyz is very fast.
How many points are you processing (v.info pt) and what are your region settings (g.region –up)?

In order to find out where time is spend yo could split upt the process into two steps:
v.out.ascii input=pt output=./tmp column=VAL
r.in.xyz input=./tmp z=4 output=pt method=sum

Cheers
Stefan


From: grass-user-bounces at lists.osgeo.org [mailto:grass-user-bounces at lists.osgeo.org] On Behalf Of patrick s.
Sent: 30. juli 2015 10:18
To: Markus Neteler
Cc: GRASS user list
Subject: Re: [GRASS-user] v.to.rast

Markus

I tested the approach you proposed, but seems to be very slow for large datasets: I am processing ~1000.000 points of observation on a 25m-Grid across Switzerland, where only few cells have multiple points inside. While v.to.rast takes a few minutes for conversion, the combination "v.out.ascii input=pt output=- column=VAL | r.in.xyz input=- z=4 output=pt method=sum" has been running for multiple hours and is still in progress.

Is there any alternative to run this conversion? I need it to run neighborhood analyses as kernel density with population field, i.e. r.neighbors in=pt out=pt_dens -c size=300 meth=sum. Maybe there is an approach to directly use the vector data and avoid conversion- something as v.neighbors meth=sum?

Thanks for you help,
Patrick

On 24.07.2015 04:13, Markus Neteler wrote:

On Thu, Jul 23, 2015 at 11:00 AM, patrick s. <patrick_gis at gmx.net><mailto:patrick_gis at gmx.net> wrote:

Dear all



I am puzzled on the behavior of v.to.rast. When several points fall into one

gridcell, the raster seems to get one value but not the sum of these. Is

there a way to sum these up instead?



Yes. I have added a related example here:



http://grass.osgeo.org/grass70/manuals/v.to.rast.html#convert-vector-points-to-raster-with-raster-cell-binning



(while it does not really fit to that manual page it is expected

there. Perhaps we need to really enhance v.to.rast to do such a job

right away).



HTH

Markus

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