Most of the data I've come across only comes in state/county/block group/block format. However, I'd like to pare down the shapefile to only observe the block groups within a city, not the county of San Diego. I have the Census ID of the block groups but don't know how to limit it to city data only.
How do I know which census tracts belong within the 2000 Census definitions of San Diego city? Suggestions?
The easiest way would probably be to use a layer with the city boundary of San Diego. You can obtain this from the SanGIS (San Diego Geographic Information Source) website.
Use the boundary layer and do a spatial selection for any census tracts that have their centroid within the city limits.
Another option would be to go to the Census.gov website and download the data files that contain address information. Link those based on the Census Tract Identifier and then select those marked within the city of San Diego.
As an aside, if you are not aware, the SanGIS website above contains a wealth of city and county geospatial data.
Hope this helps!
Additionally - brand new 2010 Census data will be available through the SanGIS/SANDAG data portal very soon. You can contact SanGIS and request a notification when it will be ready. 858-874-7000. I do not receomend using the US Census data in its raw format since they did not correct for jurisdictional boundary changes that occured over the last 10 years.
