[GRASSLIST:1869] RE: Importing Political Boundaries from TIGER

[John Gillette]

It is possible. Some areas are easy, others are harder.
It usually requires the use of extra software such as
awk.

State, county, county subdivision, place, track and block
are easy using record 1. Other polygon information using
record S is harder.

The procedure for record type 1 is to use an awk program
to separate out lines with "Left Side" not equal "Right Side".

For example:

 awk 'substr($0,171,6) != substr($0,177,6)' <tgrfile1> > <newfile1>

will separate out census tracks.  tgrfile1 is type 1 data.

Use the newfile1 (which is a subset of original data) along
with type 2 file and v.in.tig.basic to read data into Grass.  
The data will come into Grass with TLID used for each line
but the data will NOT be labeled.

Using record S would require using a data base to separate out
TLID numbers for the desired areas.  Using that list, 
v.extract would separate out the desired lines. Convert
lines to area edges and then information from record P,
Polygon Internal Point, to label the polygons.

John


-----Original Message-----
From: J. Brian Adams [mailto:brian.adams at fandm.edu]
Sent: Saturday, November 22, 2003 10:33 PM
To: grasslist at baylor.edu
Subject: [GRASSLIST:1867] Importing Political Boundaries from TIGER


I would like to import the TIGER data representing political boundaries 
such cities, townships, voting districts and the like.  The data is 
there in record types C and S, but is it possible to import these into 
a vector file?

Thanks,

Brian