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 <[email protected]>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 < > [email protected]> 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: [email protected] [mailto:postgis-users- >> > [email protected]] On Behalf Of Stephen Crawford >> > Sent: Friday, September 13, 2013 12:34 PM >> > To: [email protected] >> > 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 >> > <[email protected]> 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 >> > <[email protected]> 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> >> > >> > >> > >> > _______________________________________________ >> > postgis-users mailing list >> > [email protected] >> > http://lists.osgeo.org/cgi- >> > bin/mailman/listinfo/postgis-users >> > >> > >> > >> > >> > >> > _______________________________________________ >> > postgis-users mailing list >> > [email protected] >> > http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis- >> > users >> > >> > >> > >> > >> > >> > >> > _______________________________________________ >> > postgis-users mailing list >> > [email protected] >> > http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users >> > >> > >> > -- >> > Stephen Crawford >> > Center for Environmental Informatics >> > The Pennsylvania State University >> > [email protected] >> > 814.865.9905 >> _______________________________________________ >> postgis-users mailing list >> [email protected] >> http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users >> > > > > -- > 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 > > [email protected] > [email protected] > > 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 [email protected] [email protected] Researcher ID: http://www.researcherid.com/rid/B-4240-2009
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