Estimating downtown populations

Hello Everyone,

I am working on a project to estimate the number of people living in downtown. One of the first goals is for downtown organizations to better understand and serve its residents (e.g., a downtown residents council). We will certainly use Census 2010 count as a base line but given the new developments and undercounts of some vulnerable population, we will have to find other creative ways (e.g. utilities) that will get us closer to those numbers. Does anyone know of strategies, examples or resources of a similar project?

Best,
Gustavo.