On Tue, Sep 29, 2009 at 11:04 AM, Dave Hansen <d...@sr71.net> wrote: > On Tue, 2009-09-29 at 10:40 -0700, Scott Atwood wrote: > > 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. > > It was pretty easy using JOSM to fix the first example. The second one > appears a little less clear cut to me. > > I started out trying to fix things in a piecemeal fashion, but translating ways one at a time, but I eventually gave up and reverted my changes, because I noticed that the continuation ways of Hana Highway and all the adjoining ways seem to be affected by the same ~500 meter NNW displacement, and the magnitude of the manual adjustments was overwhelming.
The second example may appear less clear cut, because in additional to the systematic displacement to the NNW, the area around Paia seems to also be suffering the typical sorts of errors found in Tiger data: streets that are displaced or misshaped by random amounts. So even if you translated the intersection of Hana Highway and Baldwin Ave, the rest of the streets of Paia won't necessarily line up cleanly without additional manual effort. My best suggestion at this point would be to give JOSM a try. It lets > you grab much more interesting sets of data and move them around as a > group. I'm a bit hesitant to go moving large swaths of data around in > an automated way. First, I don't have any good tools to do it and it'll > take some time to code them up. Also, I'm unsure about exactly how > widespread and precise the 500m offset is. I spot checked a number of locations all around Maui, and in all the locations I checked, they seem to be affected by the same or highly similar offset to the NNW. Here is another example from the Lahaina area: http://www.openstreetmap.org/?lat=20.88606&lon=-156.68522&zoom=15&layers=B000FTF The prospect of manually shifting every single street on the entire island of Maui (even in batches within JOSM) is extremely daunting, and strongly inhibits me from wanting to do any work on Maui. And the fact that such enormous errors persist suggests to me that few if any people have done much non-automated work on Maui yet. Can we verify how much editing has been done on Maui? If it is as little as I think, there is little to loose by throwing away the existing data and starting over. I still think re-importing (or some kind of automated batch editing) might be a faster and easier way to fix the problems with Maui. -Scott -- Scott Atwood Cycle tracks will abound in Utopia. ~H.G. Wells
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