


> James Darrell McCauley writes
> 
> 
> Now, if anyone knows of a way to relate MCD (township) records in
> TIGER/Geographic Names Files to Type P records, please share.  I'm
> still pouring through Chapter 6 of the TIGER stuff, but for now I've
> got all these pretty polygons but no labels.
> 

I think your question is: how do I find a point inside the polygon
from the TIGER records so that I can use that point to label the
polygon as an area for GRASS? The answer: there is no direct way to
do it from the TIGER files. I talked to the guy at the census bureau
who is in charge of the TIGER files (I forget his name right now) and
he said the solution is that you have to calculate it yourself
because the Census Bureau's idea of a polygon for the TIGER records
and your idea of a polygon have very little to do with each other.
(Of course, you _can_ do it, since you know the edges of the polygon,
but it can be rather a pain to implement reliable code to find
an interior point [which is not identical to the centroid, which is
much easier to find].)

It is not really necessary, however, since the Census Bureau has 
already solved the problem for you. For each level of geometry in
the STF files, there is an identifying point already associated with
it. So, get the coordinates of that point by the same selection 
mechanism that you are using for any other data (e.g. population)
you want for that MCD and you are on your way. BTW, don't re-invent
the wheel here, either, since the folks at CWU have already written
software that will allow you to do this.

Eric Kostello


