[Talk-us] tiger:review=yes
Minh Nguyen
mxn at 1ec5.org
Fri Nov 28 23:03:47 GMT 2008
Alan Brown wrote:
> > On a related topic... We are asuming that some portion of tiger data
> > may never be edited as it is correct.., any feelings on how much this
> > is, or how to detect it? One approach we sre consisering is to see it
> > a road has pois along it... If so it is probably ok, I'd love other
> > ideas.
> I've noticed that almost all roads need to be repositioned in this
> area (San Jose), to properly line up ... when I was looking in the
> midwest (Indiana), however, it seems like most roads were lined up
> properly, but there was little other editting done. Do you know if
> TIGER data varies in its precision? Or if someone has just been very
> meticulous about repositioning roads in the mid-west?
>
> Some people stuck in their home might be very motivated to do that
> sort of work.
>
> In any case, I bet there's very few roads in my area that have not
> been repositioned, at minimum - or still need to be.
>
> -Alan
I think it varies by state, maybe by the original method of surveying,
which can determine how the streets are eventually laid out. Some states
are probably better than others, especially if the roadways are already
straighter and more like a grid. In southwest and southern Ohio, a
variety of surveying methods were used [1], including metes and bounds.
I've had to redraw entire townships (like tenths of counties) because
every single node was off: some by about 600 yards, others by more,
making streets go in weird directions. I've redrawn some areas in the
South Bay, and it's nothing compared to what I've seen in Ohio. I
suspect some other states are like this too.
[1] http://en.wikipedia.org/wiki/Image:Meridians-baselines.png (areas on
the map shown without a baseline were surveyed in metes and bounds)
[2] http://www.openstreetmap.org/?lat=39.36163&lon=-84.37657&zoom=15
(see the Wetherington golf course for a small example; jspeckman and I
have redone most of the surrounding area)
--
Minh Nguyen <mxn at zoomtown.com>
AIM: trycom2000; Jabber: mxn at 1ec5.org; Blog: http://notes.1ec5.org/
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