[Talk-us] Systematic errors in the Maui, Hawaii Data

[Scott Atwood]

Here's a good example from the Hana Highway:
http://www.openstreetmap.org/?lat=20.86962&lon=-156.17746&zoom=17&layers=B000FTF

There is a
distinctive set of W-shaped hairpin turns at this location.  You can
see that the OSM ways are displaced approximately 500 meters to the
north-northwest of both the satellite picture and GPS tracklogs.

Here is another example near the intersection of Hana Highway and Baldwin
Ave. in Paia (My GPS tracklog includes a brief excursion onto Baldwin Ave.
at this intersection):

http://www.openstreetmap.org/?lat=20.91837&lon=-156.38279&zoom=16&layers=B000FTF

The GPS tracklog I uploaded includes data from Wailuku in central
Maui, all along the Hana Highway as far as Waianapana State Park near
Hana.  In all the locations I spot
checked (including the ones mentioned above), there appears to be a
consistent displacement of approximately 500 meters to the north-northwest
of all ways associated with streets.  The shoreline ways appear to be more
or less accurate.

-Scott

On Tue, Sep 29, 2009 at 9:41 AM, Dave Hansen <dave at sr71.net> wrote:

> On Mon, 2009-09-28 at 23:23 -0700, Scott Atwood wrote:
> > However, as nearly as I can tell, very little work seems to have been
> > done on Maui beyond the initial Tiger upload.   The problem is, this
> > Tiger data seems to have some large systematic errors, a translation
> > to the north-northwest.  I started to manually correct a few ways
> > based on the satellite photos and GPS tracks, but I realized it would
> > probably be far better to either reimport the Maui data with a
> > correction, or apply some automated process to the existing data to
> > translate it to more-or-less the correct location.
>
> I'd really prefer not to reimport it.  Could you point us to a few areas
> where we can look at your tracks and the existing data together that
> exemplify this behavior?  Can you quantify "large systematic errors"?
>
> I really don't want to blow it away and re-upload.
>
> -- Dave
>
>


-- 
Scott Atwood

Cycle tracks will abound in Utopia.  ~H.G. Wells
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