I'm trying to generalize the attributes of a set of polygons(let's say they're census blocks with a population property) into another, overlapping set of polygons(let's say it's just a grid with no properties)
I'm certain there's a word for this problem that I've never heard of and never thought to search... If that's so, please just point me in the right direction!
I want to make a choropleth map that shows the population density of the area without showing the shape of the census blocks themselves. I want to put their attributes into the regular grid. BUT, there's of course a lot of overlap, and irregular shapes don't fit neatly within a square.
I need something that can:
- Assume that population is evenly distributed across the census block polygons.
- for each square in the grid, calculate..
- what polygons are even a little bit under it, and for each one, what portion of that irregular polygon is indeed under it.
- Then, lets say we have an irregular census block polygon that has a population of 100, and is 37% covered by the grid-block of interest... It would need to calculate the amount of the population attribute to assign to the block, in this case, exactly 37, assign it to that block, and then do the same, adding for every other shape under that block before moving on.
- Then do that for all the other polygons in the grid layer.
I should end up with the exact same total population, just abstracted and generalized into regular shapes.
How can I do this, particularly in QGIS?
I really just want to count up some point data (points in polygon) and create a choropleth corrected for population density.