Changeset: 55377588
Improve river network topology
Closed by hornbydd2
Tags
created_by | JOSM/1.5 (13265 en_GB) |
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source | None |
Discussion
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Comment from Colin Smale
Hi.... You might not be aware of this but these edits to the rivers are screwing up the admin boundaries... Can you please ensure the boundaries are complete and correct again? Example here: https://www.openstreetmap.org/relation/4253482
Any questions, please get in touch. Otherwise I expect this damage to be repaired quickly...
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Comment from hornbydd2
Hello,
I followed your link and if I have understood correctly my attempts to update the river network by breaking it at junctions is loosing the relationship with the parish boundary?
I have stopped my bulk editing and update until I can work out how to resolve this.
It looks like my edits are only affecting the streams that are also tagged as a parish.
If someone added back the parish boundary and left the new junctions as-is then this won't upset what I am doing.
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Comment from Colin Smale
It looks like where you split a way, the "old" half (which retains the original ID) is OK but the "new" part (which gets a new ID) does not inherit the relation membership. You need to make sure the relation membership is copied over. Potentially it is not just parishes, but any relation - including waterways.
As it is you that is breaking things, I think it should be you who fixes it... What is actually your goal with these edits?
Hint: if you look here in after about 1100UTC tomorrow you should see some affected admin boundaries showing up, but as I said, there may be other relations getting broken by these edits.
http://www.loach.me.uk/osm/boundaries/ -
Comment from SK53
In general such topological changes should not be done in OSM. Ideally you should create a post-processing chain which does the splits as required (large numbers of routing tools already do this for road networks). Not only is the risk of breaking other things as pointed out above; but breaking a stream into many little sections tends to make it much harder for people editing to work with. In general changing OSM data to make it easier to consume can also make it harder to maintain: it is thus usually frowned on.
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Comment from hornbydd2
I have found a plugin in JOSM that allows me to revert changes, I'm running this in the hope this undoes my edits. Interesting argument SK53, I look at the river data and a see an unusable topological nightmare. I was attempting to improve it so that it can be used by the wider scientific community for hydrological analysis free of licensing issues. OS OpenRivers is not perfect and I wanted to improve OSM. Does the idea of a "post processing chain" not break the ideology of OSM in that you feed back and improve the dataset? If I take a snapshot, improve it then no one else can share the benefits if I don't upload it?
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Comment from Paul Berry
I don't know what your exact aims are, so forgive my question, but can you not use relations to better organise the waterways? Example of my own here: https://www.openstreetmap.org/relation/7851221
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Comment from SK53
We probably ought to find a way to continue discussion elsewhere as this could be long-winded, I've long had trying OSM for hydrography models on my todo list (see http://sk53-osm.blogspot.co.uk/2014/02/floods-of-transient-data.html). The best way is to publish post-processing tools/code as open source so that anyone can do it. It's also possible to create a versioned curated extract; something I do for a couple of data sets on github (e.g., https://github.com/SK53/ua2 which is relatively complex post-processing & https://github.com/SK53/Irish-Vice-Counties which isn't at all, but versioning and consistency are needed). You can contact me by email on SK53 dot osm at gmail dot com.
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Comment from hornbydd2
I believe I have been able to revert my changes that I made today. I want to go away and discuss with others what next step should be. I'm personally for editing OSM so there is one definitive version that everyone can benefit from. Having snapshots with considerable post processing squirrelled away in github or any other site is something I would like to avoid.
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Comment from SK53
Many thanks for that.
The post-processing step is what all road routing engines do. See the recent email from Frederik Ramm on talk-gb.
It's also unlikely that you can guarantee that any additional data added will be in a topologically convenient form, or that editors will leave your split streams as is. In other words it's always best to plan for data which is not always in the most convenient format when consuming OSM data. Do drop me an email I'm interested in exploring the options.
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Comment from Colin Smale
Unfortunately it appears your reverts were not complete... And now another user (FvGordon) has started to patch up the admin boundaries but I have no idea if they are fixing ALL the broken relations. That may now complicate the revert process, This is starting to become a proper mess.
Take a look at http://www.loach.me.uk/osm/boundaries/ to see where boundary relations are affected. It is a lot of work to check and fix everything!!!
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Comment from FvGordon
Hi.. This evening I saw that many errors on http://www.loach.me.uk/osm/boundaries/ and started repairing the broken boundaries. After having repaired half of them, I saw this changeset and this discussion. Until now I have checked/repared the whole list on that site. Let's see, what errors will be shown on the next run of this tool tomorrow.
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Comment from Colin Smale
Thanks for engaging here. Could I ask you to explain your process for this? Where do you source the knowledge to make the right repairs? I have seen a couple of cases where the admin boundaries have been fixed, but other relations (for example type=waterway=river are not. My opinion is that the person who breaks these things should be given the opportunity to fix them as well - not only because it is their responsibility, but also because they need to learn something. As you know reverting a whole changeset is made much more complex when the objects have been edited in the mean time, and you seem to be on a hair-trigger sometimes, fixing stuff very quickly after it gets broken. Have you thought about having a cooling-off period of (say) 24 hours? You cannot have local knowledge of all the things you fix, so it is only fair that people who do (including the 'breaker') are given a chance as well.
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Comment from FvGordon
When there is a gap in a boundary outline ring, I can see both ends of the gap. Often a segment from an other boundary relation fits to close the gap or (in this case) the river, that he has split.
This morning I have repaired all gaps in type=waterway relations south and south-west of London. I have left type=waterway relations with gaps south east of London which he can repair. -
Comment from hornbydd2
I'm showing naivety here, I've never seen this website (http://www.loach.me.uk/osm/boundaries/) before. I was expecting to see my [offending] username all over it as someone who has broken a relationship. I was not able to find myself on it and a lot of the areas appear to be elsewhere in the UK. How does one identify the relationships I broke but may have not been fixed by the revert process? In my total ignorance it seems like there is nothing for me fix, but I guess I'm not using this website correctly?
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Comment from Colin Smale
Hi,
The reason your name is not here, is that you have NOT updated the relation when splitting a component way - and this is the exact problem. The fact that a component way (or node) has changed, does not change the relation itself. This is one of the "quirks" of OSM. However a relation in this list is there because it is considered "broken," usually because of a geometrical issue like not being a complete ring.I notice the list is empty again now - for a large part thanks to FvGordon.
- 327547270, v2
- 327547271, v2
- 327547277, v2
- 327551778, v2
- 328870562, v2
- 328870564, v2
- 328870567, v2
- 328870571, v2
- 330013463, v2
- 330023819, v2
- River Taw (330343586), v2
- Knowl Water (330367647), v2
- 330367672, v2
- 330367675, v2
Nodes (6)
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