Multiple errors in the same location

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Multiple errors in the same location

SandorS

When multiple errors appear in the same location the question is what to do?

The simplest option is, nothing. Wait until a mapper is correcting all the related errors.

Most of the detectors, inspectors, renderers, data preparation tools… select this option today. Consequently, all publicly available maps repeat the same errors what is, of course, wrong.

Let us take an illustrative example here https://osm.org/go/cCcWZjGW .

A careful analyses shows that there are several serious errors in this location. Let us mention some.

1.There are two radically different partly overlapping lakes in the location.

2.None of the lakes are close to fit into the hole in the forest area.

3.The forest and any of the lakes overlap considerably.

4.The island in one of the lakes is just partly invisible (overwritten by the other lake).

5.The obsolete natural=land tag is used for several node objects in the lakes.

6.The place=islet tag is used for several nodes without the name tag and value (so, meaningless).

If there were just a few cases like described one could contact the corresponding mappers or just make a note description on the location. Unfortunately the number of cases like the illustrated is so large that neither of the mentioned source data correction models is feasible. Yet, it is worth to mention that some data preparation chains perfectly resolves this complex error issue in their GIS or map-making systems.

Sandor

 

 

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Re: Multiple errors in the same location

Nelson A. de Oliveira
On Fri, Nov 16, 2018 at 2:08 PM SandorS <[hidden email]> wrote:
> A careful analyses shows that there are several serious errors in this location. Let us mention some.

What you are seeing is a side effect of badly/blindly importing data
and possibly without a proper discussion.

OSM already had https://www.openstreetmap.org/way/28420555
The user who did import the overlapping data should have seen this.

The user needs to be contacted, as it seems that he is still importing data.

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Re: Multiple errors in the same location

James-2
could be many things: 
1. CanVec import without corrections to todays standards
2. Old CanVec version1 imports(was pretty bad)
3. Someone added data that was already there

On Fri., Nov. 16, 2018, 11:57 a.m. Nelson A. de Oliveira <[hidden email] wrote:
On Fri, Nov 16, 2018 at 2:08 PM SandorS <[hidden email]> wrote:
> A careful analyses shows that there are several serious errors in this location. Let us mention some.

What you are seeing is a side effect of badly/blindly importing data
and possibly without a proper discussion.

OSM already had https://www.openstreetmap.org/way/28420555
The user who did import the overlapping data should have seen this.

The user needs to be contacted, as it seems that he is still importing data.

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Re: Multiple errors in the same location

Nelson A. de Oliveira
On Fri, Nov 16, 2018 at 3:13 PM James <[hidden email]> wrote:
> could be many things:
> 1. CanVec import without corrections to todays standards
> 2. Old CanVec version1 imports(was pretty bad)
> 3. Someone added data that was already there

It is a CanVec import from 4 years ago:
https://www.openstreetmap.org/changeset/23092008

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Re: Multiple errors in the same location

Mateusz Konieczny-3
In reply to this post by SandorS
16. Nov 2018 17:06 by [hidden email]:

When multiple errors appear in the same location the question is what to do?


The same as with a single error - fix the problem (how it should be done depends on situation) or


wait until it is done by someone else.


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Re: Multiple errors in the same location

SandorS

Mateusz, this was really a quick and simple answer, probably made on reading the title only.

The issue is much more complicated than you can imagine. You could really help me (and the original mapper) if you describe your suggestion how to resolve the lake and the hole mismatch in the case from the link. More precisely, assume the other mentioned problems are resolved but the (newer) lake – hole in forest fitting problem. So, how to move/transform these two objects to fit together? Further, how to do the same for really large number of cases where a manual procedure by me or “wait until it is done by someone else” is, for many reasons, unrealistic. Thanks.

 

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From: [hidden email]
Sent: søndag 18. november 2018 21:12
Cc: [hidden email]
Subject: Re: [OSM-talk] Multiple errors in the same location

 

16. Nov 2018 17:06 by [hidden email]:

When multiple errors appear in the same location the question is what to do?

 

The same as with a single error - fix the problem (how it should be done depends on situation) or

 

wait until it is done by someone else.

 


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Jem
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Re: Multiple errors in the same location

Jem
> It is a CanVec import from 4 years ago

Is there subtext to this? I saw the weird natural=wood CanVec features yesterday (polys cut up into quadtrees) and wondered about its validity. Is the CanVec import notable for being problematic?

On Wed, 21 Nov 2018 at 19:16, sandor <[hidden email]> wrote:

Mateusz, this was really a quick and simple answer, probably made on reading the title only.

The issue is much more complicated than you can imagine. You could really help me (and the original mapper) if you describe your suggestion how to resolve the lake and the hole mismatch in the case from the link. More precisely, assume the other mentioned problems are resolved but the (newer) lake – hole in forest fitting problem. So, how to move/transform these two objects to fit together? Further, how to do the same for really large number of cases where a manual procedure by me or “wait until it is done by someone else” is, for many reasons, unrealistic. Thanks.

 

Sent from Mail for Windows 10

 

From: [hidden email]
Sent: søndag 18. november 2018 21:12
Cc: [hidden email]
Subject: Re: [OSM-talk] Multiple errors in the same location

 

16. Nov 2018 17:06 by [hidden email]:

When multiple errors appear in the same location the question is what to do?

 

The same as with a single error - fix the problem (how it should be done depends on situation) or

 

wait until it is done by someone else.

 

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Re: Multiple errors in the same location

pierzen
In reply to this post by SandorS
Hi Sandor

Let me present the more general context. To represent forestry and lake areas of northern countries such as Canada,  Russia, Scandinavia, etc. is more complex then it seems. These northern territories are covered by millions of lakes surrounded by forests, have islands, with sometimes again small lakes inner these islands.
There were some imports made, duplicates created trying to follow OSM rules, a lot of ctirics and tensions, and less and less contributors ready to edit in these areas.

To see the complexity of some relations, look at the relation for Pipmuacan Resevoir https://www.openstreetmap.org/relation/381076 where there are 601 ways with inner role and 64 ways with outer role. My portable computer memory is often stressed trying to update such relaions with JOSM. Notice also that the surrouding forest around the reservoir is not yet defined.

This make me think, Can we find such complex relations in West Europe urban or rural areas? And could we reduce the complexity, the burden for mappers that contribute to OSM?

It seems that the major problem we are faced with is that rendering sofwares need to determine where they apply wood texture and that the developpers try to reduce the time to compute the information to represent adequately such areas. There were strict rules implemented recently to enforce Mutlipolygon relations.

To follow these rules represents a lot of  burden for small communities (67 contributors per day in Canada, 504 in Germany). 

I understand that developpers are also limited. But still, we should ask if the expectations about the OSM contributors are always realistic enough.

You want answers how to map. I suggest that the community should look at solutions to reduce the burden of mappers. If we could progress in the discussion between contributors and developpers and try to look at other solutions to map northern territories, I think that this would be fantastic.

It would be interesting to look if some of the burden could be transferred to softwares developpers with the objective to reduce the database size, and increase coherence and quality.    For northern forest territories, if a polygon did trace forests outer limits, could for example softwares establish the lakes, natural features, landuse areas, airports, etc which are inner the forest and should not be rendered with the forest style ?

Establish the polygons inside a polgyon and render them after this polygon ? Any other solutiojn?

Pierre


Le mercredi 21 novembre 2018 04 h 24 min 20 s HNE, sandor <[hidden email]> a écrit :


Mateusz, this was really a quick and simple answer, probably made on reading the title only.

The issue is much more complicated than you can imagine. You could really help me (and the original mapper) if you describe your suggestion how to resolve the lake and the hole mismatch in the case from the link. More precisely, assume the other mentioned problems are resolved but the (newer) lake – hole in forest fitting problem. So, how to move/transform these two objects to fit together? Further, how to do the same for really large number of cases where a manual procedure by me or “wait until it is done by someone else” is, for many reasons, unrealistic. Thanks.

 

Sent from Mail for Windows 10

 

From: [hidden email]
Sent: søndag 18. november 2018 21:12
Cc: [hidden email]
Subject: Re: [OSM-talk] Multiple errors in the same location

 

16. Nov 2018 17:06 by [hidden email]:

When multiple errors appear in the same location the question is what to do?

 

The same as with a single error - fix the problem (how it should be done depends on situation) or

 

wait until it is done by someone else.

 

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Re: Multiple errors in the same location

Mateusz Konieczny-3
22. Nov 2018 03:06 by [hidden email]:

There were some imports made, duplicates created trying to follow OSM rules, a lot of ctirics and tensions, and less and less contributors ready to edit in these areas.


Can you can give examples of duplicates created "trying to follow OSM rules" rather than created

by runaway imports discouraging editors?


I tried to edit once or twice in Canada, but before doing anything at all it was necessary to delete

massive amounts of low-quality data imported without consultation.


See http://blog.imagico.de/openstreetmap-at-its-worst for more detailed exploration

what went wrong.


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Re: Multiple errors in the same location

Mateusz Konieczny-3
In reply to this post by Jem
AFAIK yes. See for example http://blog.imagico.de/openstreetmap-at-its-worst

21. Nov 2018 23:29 by [hidden email]:

Is the CanVec import notable for being problematic?

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Re: Multiple errors in the same location

Paul Norman
In reply to this post by Jem
On 2018-11-21 2:29 PM, Jem wrote:
> > It is a CanVec import from 4 years ago
>
> Is there subtext to this? I saw the weird natural=wood CanVec features
> yesterday (polys cut up into quadtrees) and wondered about its
> validity. Is the CanVec import notable for being problematic?

Yes. CanVec is built from multiple sources, so there can be different
issues in different regions. The issues here with overlapping forest and
water geometries and overlapping data with existing data are common to
many CanVec imports. Four years ago is recent enough that the user
should have known that they needed to fix these problems. Where I live
there are problems like some data being 40-50 years old.

 From a practical side, when fixing an area, my first step is generally
to delete any data bears no resemblance to reality. In this case, if I
wanted to fix just around this lake I would do it by

1. deleting whichever of the water traces is worse;
2. getting any obvious water improvements;
3. deleting the forest inner way; and
4. adding the water as an inner to the forest multipolygon relation.

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