Rostranimin's diary

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Categorising paths

Posted by Rostranimin on 10 March 2015 in English (English)

In relation to this: draft of a tagging scheme for path categorisation.

I've been mapping actively now for 4 years, and I've tended to concentrate on paths, tracks, footways and cycleways. I think that one of the very best features of OSM is how people map these with almost as much attention as they do roads. That's something which really makes OSM stand out as different.

BUT... in mapping these features there's one thing I've really really struggled with. In places where main paths are well mapped it is possible (and desirable) to add secondary (and more) paths. When we do this all and any mapping (or data) currently becomes confusing. That's because there really isn't a well established way to record the important relationships between paths, and because 'path' covers such a huge range of features.

I've resorted to using 'tracktype' on occasion. I've done my best to map surfaces and widths, and several other features. I've used 'footway' to distinguish good quality tarmac from 'path'. All these are work-arounds... trying to solve what ought to be a simple problem. And worse, even these work-arounds cause issues. There doesn't seem to be firm agreement that 'tracktype' is properly valid on paths, that the difference between 'footway' and 'path' is as I've used it, and there's certainly no agreement on tagging things like 'smoothness'.

So while in theory I get the idea that surveying for facts is better than trying to categorise things I'm very firmly of the opinion that paths must be categorised in some way.... and yes I have looked at what's already out there. We have 'smoothness', 'tracktype', 'surface', 'incline', 'width', ideas about 'accessibility' and 'access' (e.g. wheelchair = no), there's 'sac_scale' and 'trail_visibility', and 'mtb:scale', and I'm sure I've missed lots out...

Even if I properly map just one of the larger local urban green areas/parks using each and every one of these tags I think it'll still not be possible to say for certain which are the main paths and which are the informal desire lines. Many of the main paths won't be wheelchair accessible, might not be very flat, might not be very wide, and so on... in fact some of the less formal paths might be wider than the formal ones, the informal desire lines will sometimes be flat and the formal paths steep... and those are just a few of the issues.

Of course in a bid to avoid categorising things I could not map the smaller or more informal paths at all. But that makes no sense at all... currently because I'm trying to stick to mapping facts not opinions I end up applying my opinion even more strongly... avoiding mapping some features altogether just so that maps/data remain usable.

So here's a draft of a tagging scheme for path categorisation. It's an alternative to the existing pathtype definition which doesn't seem to have much use... and this is why I've titled it with the word 'alternative' for the moment. Maybe the proper thing would have been to add it to this initial page, but this system seemed like a good way forward.

I hope at this stage to hear from people whether this scheme would work (more than any further thoughts about why this is or isn't necessary - something you'll see that I've already made my mind up on personally).

Google Map Maker

Posted by Rostranimin on 11 April 2013 in English (English)

Not a proper diary entry perhaps - but this is what's in my head so seems relevant to write: Tell me again why we don't need OSM to be accessible to lots of ordinary people... Google Map Maker is coming to the UK.

So OSM is better - but that's not the point. Remember Betamax video recorders? For those who aren't old enough... there were two formats of video recorder. One worked much better - very much better. It had powerful backers too. BUT those supporting the other made sure that it was easier to get hold of films in their format. Lots of feedback loops appeared - those wanting to watch films bought recorders for this - which made them cheaper - which made it important to supply your films in this format - which made them cheaper and which made it harder to get hold of films in the other format, and so on...

Nobody believed that the better design would lose the contest - but it did. It vanished. And we spent years with the less decent technology defining our video experience.

I'm really worried that OSM might follow suit. OSM is much better - but in general much less accessible, much better designed, but that's not the point.

For those who think that we need our front page to invite people in - for those who think we need to be really highlighting what OSM does really well - here are two links: The German OSM page translated and Openstreetbrowser (don't try to use IE with this) which is an absolutely brilliant tool - needing further development (and our support), but amazingly useful.

impassable gate?

Posted by Rostranimin on 17 February 2013 in English (English)

Anyone know how to tag a gate which is impassable (tall) and only open for a few hours a couple of times a week? No idea what the legal status is - but there's a notice on the gate.

Easter Craiglockhart Hill, Craiglockhart Pond

Posted by Rostranimin on 6 January 2013 in English (English)

My current project: Having spotted (with others) a completely incorrect path near Craiglockhart Pond (Edinburgh, UK) I decided to do some investigation. It turned out that there were some relatively big errors in other paths (incorrect path connections etc) in the area. I took initial GPS tracks and then returned a second time armed properly with camera, pen, paper etc. Difficult decisions about what to map... do we include the relatively insignificant worn paths through undergrowth or unofficial worn bits down the steep muddy hillside? I've decided to do this in some places, perhaps where this demonstrates that there's a confused network of paths - sometimes leaving a path incomplete to suggest it's partially there - and to tag paths with 'tracktype' grades to help suitable renderers to make sense of their relative significance.

Previous mapping in a tree-covered glen has helped me to work out some techniques for dealing with inaccurate GPS traces. A rather obvious thing I'd not thought of before has been to map in the winter as the trees presumably block the GPS signal less.

I've completed work on half of Easter Craiglockhart Hill (near the pond) and plan to look at the path network around the top of the hill another time. This may well be more accurate already - although I've already spotted some significant missing tracks. If anyone wants to help with this (or comment/criticise) do say so.

Isle of Colonsay

Posted by Rostranimin on 19 July 2012 in English (English)

Armed with a new (budget) GPS of my own (Garmin Etrex 20), I've combined a holiday on the Island of Colonsay with lots of recording of tracks and the like. I'm now engaged in slowly making use of this data.

Colonsay isn't well mapped, partly because what's of significance there is more the natural environment and individual buildings than the few roads and tracks. This means that small edits have a very positive effect on improving the map.

Interested to find out that my GPS tracks are consistent (on different days) in indicating a small offset on the Bing Imagery, so I'm now correcting for this.

As this is a small area with few contributors I'd be happy to hear from others who have worked on the area. I'd also like help if anyone has the time to map the buildings which can easily be seen on the Bing imagery (although please also correct for the imagery offset - Scalasaig harbour area should provide a reference for this).

Location: B8086, Upper Kilchattan, Argyll and Bute, Scotland, United Kingdom

First area mapping from survey

Posted by Rostranimin on 16 April 2012 in English (English)

I'd be very happy to receive comments on some new mapping I've been doing. West Kilbride in Ayrshire has a piece of parkland/woodland which is of significance to the town. It's difficult or impossible to map much of this from Bing images because of tree cover so I carried out a survey using two GPS devices and repeated trips along the main walkway/paths. The GPS traces give me a good shape of the paths, but there are significant errors in exact path location (obvious from variation in path traces for the same path). Have tried to use the traces, Bing imagery, and the OS opendata info for the stream path. There are errors or misalignment between all the sources of data. The Bing images are out of date, the OS opendata is well out of date, the GPS traces aren't very accurate. Clearly this makes for a bit of a challenge.

My approach has been to do the best I can in order to get this area mapped. There are outstanding questions which need to be answered - does a path actually have this shape - has the stream moved since the OS data was created - how exactly should we deal with the area where a woodland merges into a garden - what's park and what's just grass - and so on. I also know that there are areas I need to revisit to check my information - but this won't be something I'll be doing soon.

So as I say - comments welcome.


Posted by Rostranimin on 12 January 2012 in English (English)

Just a quick diary entry to mention OpenStreetBrowser. I've been using this a lot - and contributing a bit to the documentation to help new users. I think it's a fantastic service - a great help in editing - and I'm surprised not to have seen it mentioned more.

Getting started

Posted by Rostranimin on 30 March 2011 in English (English)

Have been meaning to get into OSM for ages. Success at last.
I got frustrated with Salisbury Crags in Holyrood Park in Edinburgh, UK showing up as "Cat Nick". Interesting to see how a misunderstanding spreads from one place to another. I'm wondering if changing something so obvious will cause a reaction - but tend to feel that leaping in is a good way to learn about the OSM community...

Now to the next correction - St Kentigern's ex-Church is wrongly named (although I'm a little less sure of myself on this one. How to raise the issue? Should I just jump in again...?

Location: Canonmills, New Town, City of Edinburgh, Scotland, United Kingdom
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