[Talk-GB] Somerset Levels

Sat Nov 26 09:37:22 UTC 2016

In the case of the Somerset Levels, is there actually an authoritative
boundary, or is it a fuzzy boundary like a mountain range? Are we
looking for something that doesn't exist, or is this a battle between
differing opinions?

In any case I would suggest using the source and note tags to state
where the OSM boundary comes from, such that a future mapper can judge
whether it can be improved from a better source. 

--colin 

On 2016-11-26 09:42, Jason Woollacott wrote:

> How inaccurate should something be though?   We accept that things will not be exact, and GPS tolerances and Bing offsets are a fact of life we need to accept. 
> 
> However we have proper extracts for counties/districts/Parish areas,  and all the National Parks have extracts.  
> 
> My issue with the Somerset Levels was that it wasn't the Somerset Levels, it was an interpretation of what the levels were, based on NPE contours,  (which in themselves aren't exact) and was miles and miles off in places.   If you look at the BBC link the levels stays well below Weston-Super-Mare,  yet the OSM relationship ploughed right through WSM and out the other side.   
> 
> -------------------------
> 
> FROM: Warin <61sundowner at gmail.com>
> SENT: 25 November 2016 23:23
> TO: talk-gb at openstreetmap.org
> SUBJECT: Re: [Talk-GB] Somerset Levels 
> 
> If you think that the data must be 100% accurate you will have a blank map ... therebe dragons. 
> 
> The world standard for 1 kilogram mass is an artefact (a physical object) in Paris. 
> 
> You  might think that it is 100% accurate and you'd be wrong. The surface corrodes, gets dust on it .. that adds weight .. so you polish it .. how much do you polish it? Too much and you remove weight, not enough and you leave weight behind. 
> 
> Everything has some level of uncertainty. 
> The JOSM way simplifier is set for a maximum displacement of 3 meters. Is that acceptable? 
> Remember that the original data has some level of uncertainty too. Typically a GPS would be 10 meters. Average a few and you might get down to 5 meters.
> 
> Personally I'd rather have an indication that something is there even if  'inaccurate'  ... compared to a blank bit of paper. 
> 
> On 26-Nov-16 09:18 AM, Dave F wrote: Good.
> 
> Bearing in mind that nothing* in OSM is 100% accurate (& the Somerset Levels do exist), how accurate do you need the data to be for them to be good enough for inclusion?
> 
> * No, honestly, it's not.
> 
> DaveF 
> 
> On 25/11/2016 15:12, Jason Woollacott wrote: 
> 
> in the description i remember it stated it was based on the 10ft and 25ft contours.   
> 
> -------------------------
> 
> FROM: Dave F <davefoxfac63 at btinternet.com>
> SENT: 25 November 2016 14:07
> TO: Jason Woollacott; talk-gb at openstreetmap.org
> SUBJECT: Re: [Talk-GB] Somerset Levels 
> 
> Not 100% sure, but wasn't it based on contour levels? 
> 
> On 24/11/2016 17:35, Jason Woollacott wrote: 
> 
> HI, 
> 
> Yes, I removed this as I felt that it was incorrect and did not reflect the conditions on the ground.   It was specifically  removed under one change back in September 2016, whilst I was working on addressing some of the other mapping errors around that area.     The Change was deliberately done under one change set, so that it should be easily restored if there was ever a need for it.     However the boundary was a guestimate at best and did not reflect the actual area of the Somerset Levels,  (going through Bridgwater & Weston Super Mare).   
> 
> An example of what is really defined as the Somerset Levels is here http://www.bbc.co.uk/news/uk-england-somerset-26080597 but there isn't an extract, that I've found, that we could use for tracing. 
> 
> I'm not sure what benefit reinstating this change would give.   
> 
> Jason (UniEagle) 
> 
> -------------------------
> 
> FROM: Dave F <davefoxfac63 at btinternet.com>
> SENT: 23 November 2016 12:55
> TO: talk-gb at openstreetmap.org
> SUBJECT: Re: [Talk-GB] Somerset Levels 
> 
> It appears it was deleted by user UniEagle
> http://www.openstreetmap.org/changeset/42348215
> You may wish to contact him & ask to participate in this discussion.
> 
> FYI
> Undeleting using Potlatch 1
> If you know a location where the boundary was, zoom in as close as 
> possible, then amend the URL & open in P1. This is an example near 
> Bridgwater:
> https://www.openstreetmap.org/edit?editor=potlatch&#map=16/51.1414/-2.9724
> 
> Hit the 'U' (for undelete)
> Then wait... & wait some more.
> Eventually some red lines should appear (the server can be temperamental 
> & refuse to play)
> Select the way of the relation.
> In the preset list at the bottom of the screen there should be a red box 
> with 'Click to Unlocked' written in it.
> Click to unlock (again, this may take some time)
> Save & close.
> Open your preferred editor to check it was properly undeleted.
> 
> DaveF
> 
> On 23/11/2016 00:45, Nick Austin wrote:
>> Does anyone know what happened to the Somerset Levels super-relation?
>> 
>> I don't know how to search for deleted stuff so I can't look up it's
>> history to see what happened.
>> 
>> TIA.
>> Nick.
>> 
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