So I've spent a few enjoyable (and frustrating) days teaching myself the basics of QGIS and fiddling around to try get some data output I need to drive some calculations. Sadly I'm not having any joy and am looking for ideas on how I can proceed.
What I'm trying to produce is an .xyz file of 1x1 km2 gridded population density data using Australian Bureau of Statistics (ABS) 2011 census data. The data is in the form of a polygon vector file (I'm new to GIS - hoping I've used the right terminology here). I've created population density value for each mesh block in a csv file and joined this to the mesh block layer to make a nice looking map of population density over the Greater Perth area.
This is where I'm now stuck. I need to somehow extract from this layer the average population density in every 1x1 km square over the area I'm interested in. I've tried the interpolation schemes in QGIS using polygon centroid data but that doesn't represent sparsely populated cells or ocean cells very well at all. I suspect I may have to figure out how to raster this all up (and all the problems I read are associated with rasterising a vector layer), but I'm open to suggestions on how I extract the data I need without trying to crack the nut that is rastering.
For those playing at home, these are the data sources I'm using:
- Population data: http://www.abs.gov.au/AUSSTATS/abs@.nsf/DetailsPage/2074.02011?OpenDocument
- Meshblock layer: http://www.abs.gov.au/AUSSTATS/abs@.nsf/DetailsPage/1209.0.55.0022006?OpenDocument (Western Australia Mesh Blocks Digital Boundaries in Esri Shapefile Format)