Poverty lines have been widely criticized for a long time already.
They're easy to manipulate, make millions of poor disappear, and assume that in any given country the population's living conditions is homogenous across cities and rural areas. We all know that's not the case. The consequence is that urban poverty is greatly underestimated, since the cost of life in cities is much higher than at the countryside.

Given the current state of technology it would be quite easy to review the way poverty lines are computer to create region-, province- or city-based lines and then centralize and treat the data to make it fit a unique scale. However each pack of data would come from and be designed for context-specific needs.

http://www.poverties.org/poverty-line.html