[GRASSLIST:4996] Re: US Census boundary file problem

[charles.e.dingman at census.gov]

I'm asking those who created the export files to look into this vector.  I
had loaded the e00 into ArcMap, and it did not complain or show this
vector, but then, it's not needed, topologically, to build the polygon so
it seems Arc import just discarded it.

Charles Dingman, Geographer/301-457-4307/Rm 425, WP-1
Geography Division, US Census/Washington, DC 20233-7400


|---------+---------------------------->
|         |           Radim Blazek     |
|         |           <blazek at itc.it>  |
|         |           Sent by:         |
|         |           owner-GRASSLIST at b|
|         |           aylor.edu        |
|         |                            |
|         |                            |
|         |           11/19/2002 04:37 |
|         |           AM               |
|         |                            |
|---------+---------------------------->
  >--------------------------------------------------------------------------------------------------------------------------|
  |                                                                                                                          |
  |       To:       Michael Ash <mash at econs.umass.edu>                                                                       |
  |       cc:       <GRASSLIST at baylor.edu>                                                                                   |
  |       Subject:  [GRASSLIST:4993] Re: US Census boundary file problem                                                     |
  >--------------------------------------------------------------------------------------------------------------------------|




On Monday 18 November 2002 10:44 pm, Michael Ash wrote:
> Using d.what.vect and moving due east from northern New
> Mexico, U.S.A., I find New Mexico, Nothing where Texas
> Should Be, and Oklahoma:
...
> I think that the problem is an unclosed area.

I was curious where the problem is and I found dangle on the boundary:
http://mpa.itc.it/radim/texas.png

For next occasions and others:
m.in.e00 input=st99_d00.e00 action=vector
v.support -r map=st99_d00 err=err
v.out.ascii input=err output=err

dig_ascii/err:
A  2
 26.25857424  -98.6253
 26.25219177  -98.6253

and it is also in st99_d00.e00:
      2094     12234      2039      2040       196       196         2
-9.86252999999997E+01 2.62585742374075E+01
-9.86252999999975E+01 2.62521917668542E+01

so the problem is in st99_d00.e00. I think that such dangles are
allowed in Arc/Info, but as it is not present in st99_d00.shp.
I consider it to be an error in data. You can write to census.gov.

Solution:
v.rm.dangles input=st99_d00 output=us
cp dig_att/st99_d00 dig_att/us
cp dig_cats/st99_d00.name dig_cats/us
v.support -r map=us

d.what.vect ->
-98.94589247(E) 32.37349011(N)
us in us  Area - Category 196 Texas


Radim