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Re: [osm-nyc] Bicycle Parking points

From: Chris M.
Sent on: Wednesday, July 18, 2012 11:51 AM
I don't know if there are easy answers to your questions. If you do an
import once, then users manually add more nodes of the same time, then
if you try to import again you are going to create duplicates.

If you think the city data is up to date and accurate, then you could
delete old nodes and import the entire set. There are other options,
you might be able to use RackID that the city uses, or simply date, to
eliminate some duplicates, but it would have to be an iterative
process using JOSM to verify that the the import would be correct.
Maybe it would be a neighborhood by neighborhood task.

Maybe I should have send I would attempt it with care because I think
the city data is more rich than the survey data.

On Wed, Jul 18, 2012 at 11:11 AM, Serge <[address removed]> wrote:
> Chris,
> Thanks for the feedback; your real world experience is really vital to this discussion.
> It took me a long time to really have a solid grasp on why imports are so problematic,
> but you've touched on a few of the prominent reasons, so I want to explore it a
> little.
> On Wed, Jul 18, 2012 at 10:53:28AM -0400, Chris Mcnally wrote:
>> That is because as of 2009, there may have only been one or two racks, but 2010 and
>> 2011 were big years for bike rack installation.  I noted that node[masked] was
>> accurate, and also contained some good info about the size of the rack and node
>>[masked] is accurate but it says 24 West 13th street, and I am not sure if that is
>> correct.
> Given what you've said, what's the right thing to do?
> Do you make a new bike rack node?
> Do you fix the existing node?
> Do you do something else entirely?
>> I have been adding and editing bike rack location in NYC for months now and I can
>> tell you if the DOT would update their data it would be so much easier for me to
>> import it.
> If you re-import the DOT data, you now have to do conflation, and this is where OSM
> and imports really fail.
> So let's say that in the above case, you made a new node representing the bike racks
> you found.
> How will the import process know that your data (the node you added) is present?
> Using more technical language "What can we use to conflate the two datasets?" and once
> you do conflate them, what do you do if there's a difference in the data? Eg you've
> said there are 4 bike spots, but the DOT data says there are 2?
> So if you aren't sure what the right answer is, then do you make changes at all? That
> is, knowing there's going to be an import may actually de-incentivize you from making
> the change yourself!
> Further complicating the issue, even between governmental datasets, it's often the
> case that the IDs are not kept between processes. That is ID 1000 in dataset 2012 may
> not be the same object 1000 as it was in dataset 2009.
> It's a real mess, and it's why a lot of old timers like myself are pretty down on
> imports.
> - Serge
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