[Gdal-dev] Problems with ogr2ogr and TIGER line data - California is a bit off

[Frank Warmerdam]

On Wed, 2 Feb 2005 16:08:45 -0600, Martin, Daniel A
<Daniel.A.Martin at erac.com> wrote:
> Any ideas on why this would happen?  I'm using the basic command line
> options for ogr2ogr. 

Martin,

As Ed mentions, you should check into whether there is anything
odd about the lineage of your California TIGER data.  Are you working
from raw TIGER data from the Census bureau?  All from the same year?

The TIGER data is all distributed in NAD83 decimal degrees.  There isn't
much that can go wrong with from a projection point of view.  

What coordinate system are you writing out your tab files in?  Also just
the original NAD83 or are you transforming to state plane?  There might
be ways the state plane definitions could be messed up. 

Also, TAB format scales locations to integers based on a min/max range
that is supposed to be computed based on the coordinate system.  The
default for geographic coordinates systems should be a -180 to 180 
plane and should be fine.  But if you accidentally got a projected bounding
box the resolution would likely be really crappy.  This shouldn't be
a systematic offset though, just sort of random perturbation so I doubt
this is the issue. 

My suggestion is to use ogrinfo on a known feature from TIGER and
in your TAB file to see if the coordinate match.  If they do, then it
is likely the problem is the original tiger data.  If they don't match it
is something about the translation, perhaps in the TAB code.  

If you are reprojecting the problem might be the coordinate system. 

You might want to try converting one to mid/mif and see if you get
the same issues. 

Best regards,
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