[Talk-GB] Features which move...apparently spurious edits: iD bug or "finger trouble"?

[Andy Townsend]

 > Has anyone seen something similar?  Presumably this could happen to 
nodes generally, there is no reason to think amenity=post_box is a factor.

Exactly that pattern no - but occasionally new users manage to drag 
nodes by accident.

 >  Is there any way to identify features which have moved by more than 
whatever distance might be considered "normal" for someone correcting a 
previously incorrect position?  This might be key to further 
investigation and correction.

Yes - https://www.openstreetmap.org/changeset/81021329 is an example of 
someone doing it.  I'm not sure what software they're using though; 
you'd have to ask.  The mapper who added the comment there is I think 
German, but I've had plent of conversations with them in English.

 > I can provide the node and changeset numbers if anyone wants to look 
into the details and perhaps can spot a pattern,

That might be useful so that someone can have a look.  If you don't want 
to post anything publicly you could perhaps just mail me (or anyone else 
who wants to have a look) rather than post it forever on a public 
mailing list.

 > There are some philosophical question here: which features are 
"allowed" to move and by how much?  Natural features probably shouldn't.

They do - a bit.  For example, while lowland waterways are normally a 
pretty good match for OS OpenData StreetView (which is from some time 
ago now) often their upload counterparts have changed quite considerably.

Best Regards,

Andy



On 15/02/2020 12:29, Dan Glover wrote:
> If there's a better place, please direct me appropriately...
>
> I've been using Robert Whittaker's Post Box tool to help fill gaps and 
> fix anomalies in the CT postal area. I think I've now found a pattern 
> which leads to "ghost" entries in locations where there has never been 
> a post box and leaves the actual post box either unmapped or with a 
> new node.  I have three examples where the general scenario seems to 
> have been:
>
> 1. Mapper "A" creates a node with amenity=post_box.  Other details 
> such as reference and collection time may or may not have been entered 
> at this point.
>
> 2. Time passes, possibly with edits to the node, but no change of 
> position.
>
> 3. Mapper "B" does something apparently unrelated. In the examples I 
> have seen it involves multiple ways/nodes, though not necessarily vast 
> numbers.
>
> 4. The node created at (1) is re-positioned in a fairly random manner 
> as part of the same changeset.
>
> 5. [possibly] Mapper "C" spots the missing post box and creates a new 
> node for it.  The node from (1) is still "out there", in one case it 
> was 1.3 km from the original (correct) position.
>
> Note: it transpires Mapper "A" in the three examples is the same 
> user.  Three different "B"s.
>
> I suppose the first questions are:
>
> - Has anyone seen something similar?  Presumably this could happen to 
> nodes generally, there is no reason to think amenity=post_box is a 
> factor.
>
> - Is there any way to identify features which have moved by more than 
> whatever distance might be considered "normal" for someone correcting 
> a previously incorrect position?  This might be key to further 
> investigation and correction.
>
> I can provide the node and changeset numbers if anyone wants to look 
> into the details and perhaps can spot a pattern,  The edits are by 
> three different users on widely spaced dates and the iD versions are 
> all different.  The most recent example was in September 2018, so it's 
> not likely the mapper would remember anything.
>
> Robert's tool shows the distance between OSM node and Royal Mail data, 
> which is how I found one of the examples - but it is "normal" for RM 
> data to have discrepancies, sometimes fairly significant.  The other 
> two had relatively minor offsets and were picked up through "local 
> knowledge" - but analysis of old/new position could have highlighted 
> them.  Unfortunately post boxes do get moved whilst retaining their RM 
> reference but I'd expect that to be done in OSM by creating a new node 
> and deleting the old.
>
> There are some philosophical question here: which features are 
> "allowed" to move and by how much?  Natural features probably 
> shouldn't.  Man-made ones are probably something new when they do 
> move.  Boundaries, however, are subject to revision, roads and 
> footpaths get re-aligned. Also what's an acceptable margin for a 
> correction?
>
>
> Dan
>
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