A few newbie Questions


I’m based in Bath UK

I’ve collated some queries instead of posting individual posts.

  1. What should I map a way where a path that’s walked differs from what’s indicated on an OS map? The unofficial or OS?

  2. I’ve added an area which I gave it a name. This name displays at a low zoom factor number which obliterates surrounding detail. Is there a way to specify what zoom factor it first appears in? Other areas, not created by me, have the name label first appear at a much higher zoom but appear to be labeled in a similar manner. What dictates this behavior?

  3. Pedestrian railway crossing - do I tag the track or the footpath & which should I use?
    canal wharf on an already mapped canal- separate area or redraw section

  4. What is this for?: When editing in Potlatch, there’s a canal with displays with a thicker shaded line underneath. When selected its preset key is canal then underneath in a darker than usual grey box in white lettering it say canal then names the canal. This is partially obliterated by an editable test box which is empty. Below that is the usual tags of waterway=canal & name.

  5. Is there a way to display the differences between railway bridges & a long run of raised railway arches?

  6. I have a named park bound by railings, abutting one edge is an unbounded area of grass which is bound by a road on the other side.
    How to I tag this in potlach - village green seems inappropriate. I’ve just noticed in JOSM there is a ‘grass’ option but not in poltlatch. Will JOSM still accept this attribute?

  7. How should I tag a man made duck pond in a park?

  8. What is the Level tag for? The object already has the Layer tag. Do they have different purposes?

  9. In potlatch I’ve added a weir tag (preset: weir, Waterway=weir) to a node in a navigable river way, but it doesn’t display at any zoom factor in Mapnik or Osmarender. What am i doing wrong?

  10. In JOSM the areas I download appear to be squashed in the North/South direction. Is this normal?

  11. How can I split/unglue an area in Both Potlatch & JOSM? I’ve tried the unglue & scissors commands but heither seem to work

Hope you can help me out with an answer or two.
Thanks for your patience

Dave F.

To answer some of your questions:

  1. Always map what’s on the ground, and don’t copy other maps. OS maps are copyrighted, so it is illegal to copy from them. Also, they are not necessarily accurate or up to date for some things, so better to survey it yourself.

  2. What sort of area have you added? There’s not really any way to specify what appears at each zoom - that is up to the particular renderer. The renderer should draw different things for each zoom depending on what it is tagged as, and possibly how large an area it is.

  3. The railway and the path should share a node where they cross. This node should be tagged with railway=crossing. And you can also use crossing=uncontrolled or crossing=traffic_signals to specify if there’s traffic lights etc or not.

  4. AFAIK not really. If its possible to pass under the arches, I’d say its still a bridge. You can tag it with height, for its height above the ground. Or if its an embankment tag it as embankment=yes

  5. landuse=grass is not an offical “approved” feature, but you can still use it if you want. JOSM will accept it (or any other tags), and it seems it is rendered in Mapnik and Osmarender. Or you could use landuse=meadow or natural=heath, depending on what exactly that land is.

  6. A pond or lake etc should be tagged as natural=water (even if it isn’t necessarily natural).

  7. I think level is for which floor something is on, in a building etc. Whereas layer is a relative thing, which can be used for anything, whether in a building or not.

  8. Just because a tag is in map features or in Potlatch, it doesn’t mean it will show up in the standard renderers. It seems that might be the case with weir. Though it is still worth adding them to the map, in case someone wants to make a river map, including weirs etc. Or you could file a request for it to be added to Mapnik/Osmarender.

  9. The default projection in JOSM can make things look squashed. If you change this (on Edit → Preferences → Map settings) to Mercator it should look better.

  10. In JOSM, select the node, then choose Tools → Split way, will split the area into 2 ways. To make it into 2 areas, you will have to join up the ends of the new ways.

I don’t use Potlatch, so I’ll leave those questions for someone else.

Adding a few more thoughts

(1) As Vclaw says you can’t copy an OS map. OS maps can be out of date. If you are planning an expedition and want a map to find out where footpaths are then local councils have to produce a definitive map. My local council (Hampshire) puts its on the web, but they should also be available in local libraries. The underlying map is an OS map so you can’t copy these either, but they might be useful for planning.

(2) I’d suggest contacting whoever looks after the renderer first rather than trying to adjust the tags.

(5) The bridge key is usually used with the value “yes”. But the wiki suggests other values are possible and in your case you probably want “bridge=viaduct”.

(8) The wiki has a relation called Level, which says that level refers the floor of a building something is on; whereas layer is a rule for renderers.

(9) Weirs look like they don’t get rendered. I’d suggest filing a request for them to be shown in mapnik

Sorry I forgot to reply to these.

Re Number 1.

I wasn’t very clear in making my point

Let’s say there’s a farmers field with a public footpath marker pointing diagonally across the field (As it is indicated on the OS map) but the groove that is created by previous walkers goes around the edge of the field.

Which should I map?

Re number 5

I tagged it as viaduct but it didn’t render in either Mapnik or Osmarender, so i had to revert back to bridge=yes. Another one to request maybe?

A follow on question:

Is there a sluice gate tag for a river or do i have to use weir? For example:


Dave F.

You should still not copy the OS map, but map what’s (signposted) on the ground.
I would map the path round the edge of the field, and just tag it as highway=path, plus relevant tags for surface etc.
And map the path signposted straight across the field, tag it as highway=path, plus foot=designated and designation=public_footpath. Is there any sign of a path across the field? If not, you could tag it with trail_visibility=no, plus something relevant for surface.

Also, to add - though you should not copy (most) OS maps, you can use out of copyright maps, ie NPE. They might show the path across the field that is now a right of way. You can use NPE maps as a layer in Potlatch or JOSM to trace from. Though still check it against what’s (signposted) on the ground, as not all old paths will now be rights of ways etc.

Yes, I though bridge=viaduct (or bridge=anything else) was rendered the same as bridge=yes, but checking now it doesn’t seem to be rendered (though bridge=swing is rendered in Mapnik).

  1. Can you point me to an example of what you’re talking about?

  2. quack=yes

  3. You’ll probably have to split an area at two places for it to become distinct non-area ways.

  1. I’ve since worked it out - Relations

  2. Ha, bloody ha. :slight_smile: It seems weird that there’s no man_made water feature tag.

  3. Thanks

If you feel strongly about it, feel free to use man_made=water. AFAIK, it doesn’t render but don’t let that stop you as you can use whatever tags you want in OSM.

But then you would just get debate about whether the water is natural or not (see also the recent natural=wood vs landuse=forest discussion on the talk list).

eg what is there was originally a pond there, but it has been dug out/enlarged/modified a bit. Is it still natural? I suspect most ponds in this country have been modified by man at some point in the past.
I think its best to just use natural=water for any inland body of water. Though maybe there could extra tags to describe the details of it, I’m not sure what.

Any inland body? What about reservoirs? :smiley:

I do agree with you though. Most bodies of water occurred naturally.

This one is definitely been landscaped from its concept stage (It’s on sloping ground).

I don’t fell *that *strongly about it, but as a newbie I’m still surprised at how lax the tagging is. This shows itself as a problem in many of the renders that are missing similar items because they’ve been tagged differently.

For example, have check out some of the race courses, both horse & motor. Paths, tracks, multipolygons & raceway are just some of the different ways.

The openness of our tagging is viewed by many of us as a strength, not a weakness.

I know it was only an example but racecourses aren’t really the kind of thing that are used for much else than rendering on a map in which case the exact tag matters little as long as it is rendered.

I do understand your surprise though. I’d say that nost people tag most things the same or similarly enough.
Where someone has used a really unconventional tagging scheme it will eventually be noticed by someone else and might be changed although to do so is considered rude by some contributors.