[Talk-us] How accurate is Tiger data vs Yahoo Aerial?

[Karl Newman]

On Fri, Feb 22, 2008 at 11:05 PM, Matthew Perry <perrygeo at gmail.com> wrote:

> >  I'm sure the correct fix is some real GPS readings, and align both the
> >  photos and tiger tracks to them.  But I don't have a GPS so I'm just
> >  working off the Yahoo photos.
> >
>
> Don't assume that the GPS is any more accurate than either the aerial
> photos or TIGER. Often times it takes many tracks over the same area
> to get a good lock on the average centerline.
>

I think in general it's safe to assume that a GPS will have a reasonably
accurate track. Obviously, more tracks are better, but if you have a good
lock, accuracies of 3 meters (with a 95% confidence level) are very common.
A GPS that is more than a couple years old might not lay down tracks as
accurate as this, especially where satellite reception is challenging.

Part of the reason for the highly variable accuracy of the TIGER data is
that some counties have been corrected and thus their road positions are
VERY accurate. There is a note about this (and a map about which counties
have been corrected) on the US Census TIGER data page.

Karl
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