[GRASS-user] v.to.rast

[patrick s.]

Thanks Stefan

It seems first of all v.out.ascii is slow. Following your proposaI, the 
tmp-file has only 5300 observations after 9min15s. As I have 650.000 
points this export will need approx. 18h! Can I speed this up somehow? 
(Database-driver is dbf)

Patrick

P.S. g.region -up & v.info are given below.


##g.region -up
projection: 99 (Swiss. Obl. Mercator)
zone:       0
datum:      ch1903
ellipsoid:  bessel
north:      1297000
south:      1074200
west:       2484400
east:       2834800
nsres:      25
ewres:      25
rows:       8912
cols:       14016
cells:      124910592

##v.info
  Number of points:       647957          Number of centroids: 0          |
  |   Number of lines:        0               Number of boundaries: 
0          |
  |   Number of areas:        0               Number of islands: 
0          |
  | |
  |   Map is 3D: No                                               |
  |   Number of dblinks: 1                                                |
  | |
  |   Projection: Swiss. Obl. 
Mercator                                         |
  | |
  |               N:           1294822    S: 1075554                 |
  |               E:           2831184    W:           2486245


On 30.07.2015 13:59, Blumentrath, Stefan wrote:
>
> 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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