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#1 2012-11-23 22:44:25

OS Opendata contours

Has anyone managed to convert the OS Opendata 'panorama' .dxf files into usable UK contour maps? As far as I can see these are considerably more detailed than the SRTM DEM 'roll your own' contour models (albeit UK only), but are in a seriously tacky autocad format. The OS DEM model is more amenable to manipulation, but then you have to roll your own contours again, which seems daft when the OS DEM data is derived from the contours in the first place. I can smooth and interpolate and extrapolate lots and lots (I did) and also wind in spotheight data and heights from GPS tracks, but frankly the hand drawn OS contours are probably still the best (if you spot and fix the odd labelling errors - e.. 240m contour lines labelled at 140m).

While on the OPENDATA topic, does anyone happen to have a pointer to just how much of this is already rolled up into the OSM maps for the UK? AFAICT OS road data is pretty useless, being cut everytime it goes under a bridge or whatever, but is looks like water, admin boundary, placenames, land cover etc is all good data .. but maybe already included?

And thirdly (GSVs always come in 3s), is the 'cROW' access land polygon data already included? This (like OS vector data) is available in nice tractable ESRI format (although the access land boundary is rather a stinker, in that it contains about 5x more points than it needs to, wrapped up at just a few (10?) objects with thousands of components in each object.

p.s. I tried the talk_uK mailing list but it appears to be morbid, or at least moribund .. I guess forums have won.

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#2 2012-11-24 15:25:46

Vclaw
Senior Member
From: Alba
Registered: 2009-02-25
Posts: 481
Website

Re: OS Opendata contours

Not sure what mailing list you are referring to - the Talk-GB mailing list is fairly active, busier than this forum anyway. http://lists.openstreetmap.org/listinfo/talk-gb

For OS Opendata contours, some instructions here for converting into Garmin format: http://wiki.openstreetmap.org/wiki/OS_O … _on_Garmin

In terms of how much OpenData is in OSM, probably quite a bit. Though it should not be added in bulk imports, instead merged and connected with what is already there, and checking against other sources (survey, aerial imagery, etc) where possible.
As you say, roads are not very useful, as they are often broken. It is probably easier and more accurate to just trace from aerial imagery and GPS tracks. Plus most roads are mapped in OSM already, including details not in OS data (names, speed limits, lanes etc).
Yes, water can be useful, especially for things not obvious on aerial imagery (eg small streams under trees). Though it does need to be tidied up a bit before adding, eg rivers can be broken under bridges or the edge of grid squares. Plus it may have excessive numbers of points in places. I'm not sure how accurate it is to have thousands of points for a river outline, which may be regularly changing.

The OpenData admin boundaries are very useful, as there isn't really any other way of mapping them. So they were not (usually) not mapped in OSM previously. They have been added for some parts of UK.

For access land, I assume you mean the Natural England data? It has been discussed on the mailing lists previously, but I don't know if anything is happening with that.

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#3 2012-11-25 14:56:55

Re: OS Opendata contours

I tried the talk-GB mailing list and had no reply from supposed list owner after several days so I gave up (I had an email address problem so my posting got held for moderation, and never came out).

I noted that the opendata (panorama) contours are at the 'all you gotta do is .. ' stage, I just wondered if anyone had actually DONE. Apparently not. OK here is a sample of one small area (I don't have a C++ compiler here so I winged it):

www.quik.clara.co.uk/so88.zip

(unzip it you get a .mp file which you can view with (free) gpsmapedit .. if folks need a version for JOSM I can probably convert). I wonder how it compares with the current SRTM maps (in peoples' opinions - I have my own, obviously). The alternative is to re-contour from the OS DEM data, but that is only marginally more detailed than the SRTM version (50m grid whereas SRTM is pretty much 60x90m grid for hereabouts). The OS DXF files contain sundry other stuff which I tried hard to ignore .. probably should have ignored shorelines, breaklines, and ridgelines too. If people think the results are useful, maybe we'll have an SMC contour maps version 3.0 (if I live long enough).

I understand about not uploading bulk OS data, but I can't see an easy way of manually adding stuff which spans mega-areas (admin boundaries, right to roam lands etc.). Seems to me that adding it piecemeal is likely to cause more problems than a bulk addition (which is then amenable to a bulk update, or removal, or re-tagging or whatever). I shall consider to ponder, and await comments (if any). Actually I think admin boundaries are a bit of a PITA and would be better as polygon/areas
(Parish, County, whatever) .. knowing where the border is is only half the problem if you don't know what the two sides actually are.

Yes, OS water data is (still) a mess, but better than the alpha release. Biggest niggle for me (apart from the breaks, which are only a pain when it comes to naming) is the fact that a lot of the water is shown as polygons (PLUS the boundary lines. 8<.) .. and there's no distinguishing lakes from rivers (plus the labels are typically dots miles away). If they did roads like that there's be a long thin 'made made area' polygon for the M6, with a label saying 'M6' someplace in the vicinity of Stoke. Oh wait, I mustn't give them ideas.....

Why would anyone care about water - well FPs trip over it quite a lot, and the presence (and functioning) or bridges and culverts is sort of important. It also is a useful, fairly easily observed, navigational aid "(If my feet are wet I am probably standing in the lake at X,Y").

What I'm really aiming to do (when I get a spare year) is to upload as much as possible of my Shropshire Rights of Way survey data - separate message required I think.

D.

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#4 2012-11-25 15:52:56

Vclaw
Senior Member
From: Alba
Registered: 2009-02-25
Posts: 481
Website

Re: OS Opendata contours

I think you have to be subscribed to the mailing list before you can post to it (using the same email address). Otherwise it is held for moderation, I'm not sure how often the moderation queue is checked.

For contours, also see that talk page: http://wiki.openstreetmap.org/wiki/Talk … _on_Garmin
User Tms13 says he has produced a Garmin img file, and has posted a link to it, but the link is now broken. You could send him a message and ask if its available anywhere.

For admin boundaries, they should probably be done about a county at a time. And they should be mapped as boundary relations. ie one relation for the county, with sections of the boundary mapped as ways, as members of the relation. So boundaries of neighbouring counties would be a member of a relation for each. See http://wiki.openstreetmap.org/wiki/Relation:boundary

For water, it may be easiest just to get the names from other sources, eg OS StreetView. Also note that small streams are usually just mapped in OSM as a line for the centre of a stream, not as an area. Larger rivers should be mapped as a centreline as well as an area for the edge of the riverbanks. Whereas I think the OS data just has them as areas.

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#5 2012-11-26 17:18:46

Re: OS Opendata contours

Yes, the 'different email address' was my problem, and the moderation queue is apparently write-only. 8>.

Can't find any comments / agreement on the usefulness or otherwise of OSGB contours (hand drawn). I guess I'll convert a grid square or two and see if anyone wants to eyeball them.If anyone has a favourite area, let me know (OS grid square .. I like SO, but then I live there).

Not sure I'd agree on mapping boundaries as ways, I'd personally rather have a polygon (for parish, county, country, whatever). That way I can (with considerable heavy lifting in the computing department) do things like 'if <object> is in <parish>.
I guess a compromise would be to have both.

Yes, OS water data is a PITA .. I know just what it looks like. It looks OK rendered on a handset, but from a labelling perspective it's hopeless (and 'downstream' in a polygon is not very useful). Maybe I'll write a script to at least strip out the lines which are repeats of polygon boundaries.

I think I'll convert some Opendata and try it as overlays for OSM maps (as contours already are, iirc) .. that way I won't mess with anyone's data. Paths/etc do need to be wrapped in at some point, but that's going to be major effort with some 15,000 path sections (4,000 km) and probably 50k or 60k point data items (gates, stiles, waymarks, bridges, problems, fords, etc).

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#6 2012-11-27 22:46:50

Vclaw
Senior Member
From: Alba
Registered: 2009-02-25
Posts: 481
Website

Re: OS Opendata contours

GSV3MiaC wrote:

Not sure I'd agree on mapping boundaries as ways, I'd personally rather have a polygon (for parish, county, country, whatever). That way I can (with considerable heavy lifting in the computing department) do things like 'if <object> is in <parish>.
I guess a compromise would be to have both.

Sections of the boundary are mapped as ways, but they are all part of a boundary relation. So the relation should make a closed polygon. And you can do queries to find things within a boundary relation.
See the wiki for details on relations, specifically boundary relations / multipolygon relations: http://wiki.openstreetmap.org/wiki/Relation

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#7 2012-11-28 21:02:28

Richard
Senior Member
From: Charlbury, UK
Registered: 2007-04-24
Posts: 255
Website

Re: OS Opendata contours

GSV3MiaC wrote:

Yes, the 'different email address' was my problem, and the moderation queue is apparently write-only.

That's pretty much always the case with mailing lists... too many would-be spammers to keep a very close eye on the queues. sad

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#8 2012-12-01 17:05:42

Re: OS Opendata contours

Vclaw wrote:
GSV3MiaC wrote:

Not sure I'd agree on mapping boundaries as ways, I'd personally rather have a polygon (for parish, county, country, whatever). That way I can (with considerable heavy lifting in the computing department) do things like 'if <object> is in <parish>.
I guess a compromise would be to have both.

Sections of the boundary are mapped as ways, but they are all part of a boundary relation. So the relation should make a closed polygon. And you can do queries to find things within a boundary relation.
See the wiki for details on relations, specifically boundary relations / multipolygon relations: http://wiki.openstreetmap.org/wiki/Relation

That's cool then, I'll just chop the boundaries up into appropriate pieces (right now the OS ones run past 'junction points' willy-nilly), and glue them back (if required0 with a relationship. I doubt anyone is too excited about the boundaries of Abdon Parish, except maybe me.

No feedback either way on the usefulness of OS (as opposed to SRTM derived) contours .. I think I'll proceed to convert the whole country to Garmin format anyway, since the PC is not busy today. (Obviously is IS only the whole country, even N Ireland doesn't get a look in, on the Opendata front, much less Eire etc.).

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#9 2012-12-01 17:06:40

Re: OS Opendata contours

Richard wrote:
GSV3MiaC wrote:

Yes, the 'different email address' was my problem, and the moderation queue is apparently write-only.

That's pretty much always the case with mailing lists... too many would-be spammers to keep a very close eye on the queues. sad

Well I did actually email the list owner directly, and got no reply to that either, at which point I gave up.

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