How can we improve the speed of the functionst_worldtorastercoordx(rast,geom)[

Hi Pierre:   
   I am a project manager of chinamobile HubeI ,recently we are woking on a mini-project to verify the Raster function of PostGIS 2.1.

    Raster DATA is such an advanced data model, therefor it is so difficult to find some materials on the project of  Raster DATA . Thanks to the GOD, I find your web-site in the university LAVAL and the Le Centre d’étude de la forêt ( I know a little francs) , I carefulread the ppt <<Stockage, manipulation et analyse de données matricielles avec PostGIS Raster>>, And I get to know the methods about the raster creation function. Thank you so much for all your
materials on the web-site, it help me to step on step future in the area of advanved Spatial analysis technology. Just like you have said , form vector to Raster. By the way, I work in the wireless netwok management deparement. Our daily work rely heavly on the tools MAPinfo, which is realy a hard labor job , especially for some SPatial analysis task. Now I get to know more about PostGIS. In the future, I will transfer all the Job form MAPinfo to PostGIS. How I can learn from you in the future. 

     With the help of your document, it took us more than 3 weeks to finish the project. yet we have a  problem on the function  st_worldtorastercoordx(rast,geom).
    the commands are
update atu_sample set x =st_worldtorastercoordx(rast,geom) from myrasters;

update atu_sample set y =st_worldtorastercoordy(rast,geom) from myrasters;

       In the above example , we have 12000 points and a 1327* 1555 (pixels) raster data . it takes more than 160 Seconds to finish the task. In the future project, we will have more than 1200000 points , how could we fix the Performance problem?

      hope you could help us to fix the problem ,  and do please keep in touch.

     what is more , I send you a doucment on our mini-project. you can konw more on our project.

zhanying



Hi,

   Why do you extract the raster coordinates? What do you do with it afterward?

   To make the query faster you could simply do the math yourself without relying on the ST_WorldToRasterCoord() function.


Pierre