hi all,
i’m interested in estimating the centre of population of a city and how it might have changed in 10 years. i have a vector polygon layer for each year, which is the ward population. each layer has 198 polygons(wards) with population attributes for each polygon(ward). The distribution of population within a ward is not known, hence assumed uniform for now.
is there a module in GRASS for calculating this. i know we can calculate geographic centroids, but was’nt sure if there was one for this kind of thing.
Otherwise i could do it manually by extracting the geographic centroid of each polygon, then the coordinates of the population centre would be:
xhat = sum(Pi Xi) /(sum(Pi)
yhat = sum(Pi Yi) / sum(Pi)
where Xi, Yi are each polygon i’s geographic centroids; and Pi are each polygon’s population
coordinates are in UTM.
what do you think?
Thanks,
Vishal
Vishal K. Mehta, PhD
Scientist
Stockholm Environment Institute - US
133 D St Suite F
Davis CA 95616
www.sei-us.org