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</o:shapelayout></xml><![endif]--></head><body lang=PT-BR link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span lang=EN-US>I have a raster with one band that represents the deforested area in the Amazon. This raster has 13 categories representing the deforested area in each year from 2001 to 2013.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US>Beyond this raster data, i have a database with 800 polygons that represents 800 cities of the Amazon region.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US>My interest is calculate the total deforested area in each city of the region for each year. In other words, i need to calculate the intersection area between the raster and the polygons database for each category of the raster.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US>In this scenario, i have two main questions:<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US>1 - What's the best way to do raster/polygon intersections? I read about two different approaches, one using ST_Intersection and the other one using ST_Clip. The second one apparently is faster and more efficient, but i don't know about its precision.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-US><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-US>2 - Assuming that i used ST_Clip to do the intersections, the result it’s gonna be another raster. How can i calculate the area of each category of this raster?<o:p></o:p></span></p></div></body></html>