[Talk-us] Talk-us Digest, Vol 82, Issue 31

Reilly, Colin creilly at doitt.nyc.gov
Fri Sep 19 18:28:45 UTC 2014


" All that a particular data source can be authoritative for is what that data source says something is. What is authoritative for OSM is the ground truth."

Not sure I understand the first sentence. As for the second, your eyes can deceive you. Nonetheless, I would argue that authoritative data should matter and could be tagged as source= authoritative. Intent not to prevent other from updating but more as a cautionary flag.  To me accuracy and currency should be paramount.  

" This seems incorrect. If I build a structure on two tax parcels, it can exist as a single building. It may not be legal, or may require planning tricks that make it two buildings in the eyes of the city, but if I survey it and it's one building, I will map it so."

Not in NYC. Although there are some edge and legacy cases, you cannot legally build a building that straddles more than one parcel. You would first need to merge the tax parcels before constructing the building. 

" Yah, if that were true it would be a very strange and site-specific rule. I know of several buildings here that span multiple tax lots."

NYC specific. I was not speaking in general terms but to NYC building/finance codes. Without that requirement, code enforcement and tax assessment would be difficult.

 

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Today's Topics:

   1. Re: Merging NYC buildings (Bryan Housel)
   2. Re: Merging NYC buildings (Paul Norman)
   3. Re: Merging NYC buildings (Paul Norman)
   4. Re: Merging NYC buildings (Darrell Fuhriman)
   5. Re: Merging NYC buildings (Martin Koppenhoefer)


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Message: 1
Date: Fri, 19 Sep 2014 10:00:37 -0400
From: Bryan Housel <bryan at 7thposition.com>
To: "Reilly, Colin" <creilly at doitt.nyc.gov>
Cc: Katie Filbert <filbertk at gmail.com>, "talk-us at openstreetmap.org"
	<talk-us at openstreetmap.org>
Subject: Re: [Talk-us] Merging NYC buildings
Message-ID: <CA453D20-5685-44DB-A9DC-4AB2F6C41FED at 7thposition.com>
Content-Type: text/plain; charset="windows-1252"

Nice!  (I worked on a project for the NYC Law Department involving nycitymap last year.)

I think your best option is to reach out to the user directly (it seems like just one person adding 3d details) and tell them not to adjust the building footprints.

We really should come up with a good way to make authoritative data harder to edit in the various editors.
Maybe something like a  `DONTFIXME=yes` tag that locks the feature in place?   




On Sep 19, 2014, at 9:49 AM, Reilly, Colin <creilly at doitt.nyc.gov> wrote:

> No, unfortunately we cannot but I haven’t given up on my attempts to gain clearance.
>  
> However in this case the imagery doesn’t really help. See link below which gives you a general idea of what we see internally. Note the shade cast by the building to the east. In this case it was the tax parcel and multiple address that indicate two buildings not one.
>  
> http://maps.nyc.gov/doitt/nycitymap/?z=10&p=992999,215996&c=GIS2012&s=
> a:926,3+AVENUE,MANHATTAN
>  
> Colin
>  
> From: Katie Filbert [mailto:filbertk at gmail.com]
> Sent: Friday, September 19, 2014 9:36 AM
> To: Reilly, Colin
> Cc: talk-us at openstreetmap.org
> Subject: Re: [Talk-us] Merging NYC buildings
>  
> On Fri, Sep 19, 2014 at 3:19 PM, Reilly, Colin <creilly at doitt.nyc.gov> wrote:
> I’ve also see buildings merged that may appear to be one building from above but are in fact two.
>  
> Do you have better imagery that we would be able to use? I think that would help in this case.
>  
> Cheers,
> Katie
>  
>  
> A single building cannot straddle two tax parcels. In general, visual information in NYC is sometimes not enough to warrant a change. Example below of a building with two separate address points sitting on two separate tax parcels that was merged when it should not have been.
>  
> The intention of this email is to inform the group. I’m sure you can all imagine the challenges in managing data in Manhattan. Often multiple sources are necessary to validate changes.
>  
> http://www.openstreetmap.org/node/3069855105/history#map=19/40.75931/-
> 73.96838
>  
> Cheers,
>  
> Colin Reilly
> Director, Geographic Information Systems New York City Department of 
> Information Technology & Telecommunications
> 
> _______________________________________________
> Talk-us mailing list
> Talk-us at openstreetmap.org
> https://lists.openstreetmap.org/listinfo/talk-us
> 
> 
> 
>  
> --
> Katie Filbert
> filbertk at gmail.com
> @filbertkm / @wikidata
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Message: 2
Date: Fri, 19 Sep 2014 09:06:31 -0700
From: Paul Norman <penorman at mac.com>
To: talk-us at openstreetmap.org
Subject: Re: [Talk-us] Merging NYC buildings
Message-ID: <541C5487.7000901 at mac.com>
Content-Type: text/plain; charset=utf-8; format=flowed

On 9/19/2014 7:00 AM, Bryan Housel wrote:
> We really should come up with a good way to make authoritative data 
> harder to edit in the various editors.
All that a particular data source can be authoritative for is what that data source says something is. What is authoritative for OSM is the ground truth.

That's not to say that there aren't features that would be difficult to improve in accuracy. The Canada-US border on the west coast comes to mind. It's pieced together from multiple observations and data sources and it's unlikely someone could improve it's accuracy, but the possibility remains there.

The idea of some tag to "lock" objects from normal editing because they are "authoritative" has occasionally been proposed, and to summarize the discussion, it's extremely unlikely to happen.



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Message: 3
Date: Fri, 19 Sep 2014 09:26:25 -0700
From: Paul Norman <penorman at mac.com>
To: talk-us at openstreetmap.org
Subject: Re: [Talk-us] Merging NYC buildings
Message-ID: <541C5931.80309 at mac.com>
Content-Type: text/plain; charset=utf-8; format=flowed

On 9/19/2014 6:19 AM, Reilly, Colin wrote:
> A single building cannot straddle two tax parcels.
This seems incorrect. If I build a structure on two tax parcels, it can exist as a single building. It may not be legal, or may require planning tricks that make it two buildings in the eyes of the city, but if I survey it and it's one building, I will map it so.

In dense urban areas the edges of buildings can often only be determined by surveys, not by imagery, as the imagery only shows the roofs generally, and roofs may change appearance within a building or not change appearance between two adjacent buildings.



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Message: 4
Date: Fri, 19 Sep 2014 09:35:18 -0700
From: Darrell Fuhriman <darrell at garnix.org>
To: Paul Norman <penorman at mac.com>
Cc: talk-us at openstreetmap.org
Subject: Re: [Talk-us] Merging NYC buildings
Message-ID: <80377E08-F9F9-49B5-9B40-BF4A246A4BDA at garnix.org>
Content-Type: text/plain; charset=us-ascii

Yah, if that were true it would be a very strange and site-specific rule. I know of several buildings here that span multiple tax lots.

d.

On Sep 19, 2014, at 09:26, Paul Norman <penorman at mac.com> wrote:

> On 9/19/2014 6:19 AM, Reilly, Colin wrote:
>> A single building cannot straddle two tax parcels.
> This seems incorrect. If I build a structure on two tax parcels, it can exist as a single building. It may not be legal, or may require planning tricks that make it two buildings in the eyes of the city, but if I survey it and it's one building, I will map it so.
> 
> In dense urban areas the edges of buildings can often only be determined by surveys, not by imagery, as the imagery only shows the roofs generally, and roofs may change appearance within a building or not change appearance between two adjacent buildings.
> 
> _______________________________________________
> Talk-us mailing list
> Talk-us at openstreetmap.org
> https://lists.openstreetmap.org/listinfo/talk-us




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Message: 5
Date: Fri, 19 Sep 2014 19:09:06 +0200
From: Martin Koppenhoefer <dieterdreist at gmail.com>
To: Paul Norman <penorman at mac.com>
Cc: osm <talk-us at openstreetmap.org>
Subject: Re: [Talk-us] Merging NYC buildings
Message-ID:
	<CABPTjTDM0QjYOnT-GakW5=X09-GOMPz2xO2crCC=imEPU2eDJw at mail.gmail.com>
Content-Type: text/plain; charset="utf-8"

2014-09-19 18:26 GMT+02:00 Paul Norman <penorman at mac.com>:

> but if I survey it and it's one building, I will map it so.
>


Does this survey include the inside or will the judgement be based only on the outside?



>
> In dense urban areas the edges of buildings can often only be 
> determined by surveys, not by imagery, as the imagery only shows the 
> roofs generally, and roofs may change appearance within a building or 
> not change appearance between two adjacent buildings.
>


Typically there will be some kind of division in the roof because you have to avoid fire going from one building to the other.
I think it is more probable that people will split one building into several buildings than the other way round.

It may also not be very clear how many buildings there are in some cases, e.g. when dealing with very old buildings (i.e. not built according to modern prescriptions), sometimes you will have dependent buildings (you can't tear down one building because the neighbour would fall as well because it is leaning on the other building, something that today won't be allowed under any jurisdiction I am aware of).

cheers,
Martin
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