[postgis-users] tile size
Duncan Golicher
dgolicher at gmail.com
Thu Sep 19 16:55:21 PDT 2013
Here is a simple speed test using R system.time to record the result after
reloading the same raster with different tile sizes.
https://dl.dropboxusercontent.com/u/2703650/SpeedTest.html
Not had any time to anotate or explain the code but the test should be
easily replicable (at least under Ubuntu). I provide a link to the data
(which was used in the example on the geostat course). The code only runs
without modification on Linux as I use system to send commands pasted
toegether in R to the shell. Also needs unix odbc setting up.
Note that the point on raster overlay can be beaten easily for speed by the
extract function in the R raster package. However the polygon overlays are
now very fast and compare well with any alternative way of getting the
result. Using PLR to run R functions within PostGIS is great if you want
medians, quartiles etc or any other derived property.
Duncan
On Thu, Sep 19, 2013 at 4:32 PM, Duncan Golicher <dgolicher at gmail.com>wrote:
> Out of interest I quickly checked whether the conclusions still hold for
> PostGIS2.2.
> The changes made in ST_Clip, and some other functions including st_value
> seem to have altered not just the absolute timing (much faster) but also
> the relative timing of operations as a function of tile size.
> Point on raster overlays are now slower when tile size is small (<50
> pixels), whereas previously there was an almost linear increase with tile
> size. Bborie may be able to explain why this change has occurred. I will
> try to add an update to the weblog at some point in order to clarify the
> sitation. It is GOOD NEWS as apparently there is now a single optimum tile
> size for both polygon and point overlays and this does seem to lie at
> around 200 - 300 pixels using the same example as the weblog, although I
> have not run enough tests to confirm this. I'll try to find time to confirm
> this.
>
> Duncan
>
>
>
>
>
> On Thu, Sep 19, 2013 at 10:36 AM, Pierre Racine <
> Pierre.Racine at sbf.ulaval.ca> wrote:
>
>> You can also have a look at this article from Duncan Golicher if you are
>> doing raster/vector analysis:
>>
>>
>> http://duncanjg.wordpress.com/2012/10/30/tile-size-for-raster-vector-overlays-in-postgis/
>>
>> > -----Original Message-----
>> > From: postgis-users-bounces at lists.osgeo.org [mailto:postgis-users-
>> > bounces at lists.osgeo.org] On Behalf Of Stephen Crawford
>> > Sent: Friday, September 13, 2013 12:34 PM
>> > To: postgis-users at lists.osgeo.org
>> > Subject: Re: [postgis-users] tile size
>> >
>> > OK, thanks. I will give that a try.
>> >
>> >
>> >
>> > On 9/13/2013 12:31 PM, Adam Eskreis wrote:
>> >
>> >
>> > The most common tile size that I've seen in production is 256x256
>> >
>> >
>> > On Fri, Sep 13, 2013 at 10:33 AM, Bborie Park
>> > <dustymugs at gmail.com> wrote:
>> >
>> >
>> > Steve,
>> >
>> > There really isn't. What I do recommend is that if your
>> raster
>> > data is not going to change over time (and you don't need to replicate
>> the
>> > database), load them as out-db rasters. That way, you can easily change
>> tile
>> > size within the database with ST_Tile.
>> >
>> >
>> >
>> > -bborie
>> >
>> >
>> > On Fri, Sep 13, 2013 at 6:06 AM, Stephen Crawford
>> > <src176 at psu.edu> wrote:
>> >
>> >
>> > Hi All,
>> >
>> > Is there a rule of thumb for determining the best
>> tile
>> > size when tiling a raster?
>> >
>> > Thanks,
>> > Steve
>> >
>> >
>> > --
>> > Stephen Crawford
>> > Center for Environmental Informatics
>> > The Pennsylvania State University
>> > <tel:814.865.9905>
>> >
>> >
>> >
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>> >
>> >
>> >
>> >
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>> >
>> > --
>> > Stephen Crawford
>> > Center for Environmental Informatics
>> > The Pennsylvania State University
>> > src176 at psu.edu
>> > 814.865.9905
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>
>
>
> --
> Dr Duncan Golicher
> Investigador Titular,
> El Colegio de la Frontera Sur, Chiapas,Mexico
> Mexico tel +52 1 967 137 94 20
> Skype name duncangolicher
>
> Publications: http://www.mendeley.com/profiles/duncan-golicher
>
> Senior lecturer, Bournemouth University, UK
> Centre for Conservation Ecology & Environmental Change
> School of Applied Sciences
> Christchurch House rm C218a
> Bournemouth University
> Fern Barrow
> Poole (Dorset) BH12 5BB UK
> Tel. +44 (0)1202 961682
>
> For list of publications see Researcher ID:
> http://www.researcherid.com/rid/B-4240-2009
>
> dgolicher at bournemouth.ac.uk
> dgoliche at ecosur.mx
>
> Researcher ID:
> http://www.researcherid.com/rid/B-4240-2009
>
--
Dr Duncan Golicher
Investigador Titular,
El Colegio de la Frontera Sur, Chiapas,Mexico
Mexico tel +52 1 967 137 94 20
Skype name duncangolicher
Publications: http://www.mendeley.com/profiles/duncan-golicher
Senior lecturer, Bournemouth University, UK
Centre for Conservation Ecology & Environmental Change
School of Applied Sciences
Christchurch House rm C218a
Bournemouth University
Fern Barrow
Poole (Dorset) BH12 5BB UK
Tel. +44 (0)1202 961682
For list of publications see Researcher ID:
http://www.researcherid.com/rid/B-4240-2009
dgolicher at bournemouth.ac.uk
dgoliche at ecosur.mx
Researcher ID:
http://www.researcherid.com/rid/B-4240-2009
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