Friday, 15 April 2016

qgis - Calculate population coverage?



I am relatively new to QGIS.


I am looking at the percentage of an population that has geographical access to healthcare. Therefore I have one shapefile with village boundaries including population number of each village. Another shapefile is all Healthcare facilities in the area buffered with 5km zones. I now want to calculate the percentage of the village area that is covered by the Healthcare facility buffers and multiply this by the my population numbers.


I did manage to create an intersect shapefile of the two formal shapefiles that created correct new polygons of intersection per village. I now, however, do not know how to sum the areas (Area_1) of all these buffer polygons which are coded equally in the attributable table (under P_06_ID) and divide this by the total village area (AREA). And then multiply this number by the population (Population).


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The command does indeed calculate the percentage of the population that overlaps with that specific polygon. However it still does not sum the different polygons.


output after command


So what I now want to do is to sum those numbers with the same parish ID automatically (I do have around 500 parishes). So in this example sum PopPerc from cell 699- 709.


Any suggestions?





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