[talk-au] General Observations.

Ross Scanlon info at 4x4falcon.com
Sun May 9 09:59:25 BST 2010


Hi All,

Some general observations on the state of mapping following on from the reverts of the Perth area items.

I'm not looking at discussing these, I'm just advising that if you are mapping then these things need to be taken into account.


1. Intersections

-  All way intersections need some form of information.
-  If it's two highway=* ways then there has to be a node there joining the two highway=* ways, unless its a bridge or tunnel.  If it's a bridge or tunnel it needs an appropriate layer=* tag.  It's no use just drawing one road crossing another without having the intersection node.  Josm and potlatch both show you when the way you are drawing will connect to the way you want to connect it to.  In josm you can set it up so that the junction nodes are highlighted in a different colour to other nodes so it's easier to see them.


2. Areas

-  Landuse in particular.  Don't join it to the road ways.  A lot of the reverts would not complete as the nodes on the areas were nodes on the false roads and in some cases were on real roads as well.  It became extremly time consuming to sort them out.
-  If you are tracing nearmap imagery for landuse then use boundary fences for the positioning of the edges, not the edges of roads.  If there's no boundary fence then the landside of the footpath.  While I was checking the reverts I had to move a lot of landuse boundaries as they had been drawn along the roads near them but are tagged as source=nearmap,  some the actual boundary fence of the landuse was clearly visible 100m away from where the line had been drawn.  Remember the boundary is the landuse area, not the road reserve.
-  Have a look at Auckland NZ for some really excellent landuse mapping.

3. Oneway errors.

-  There are lots of these occuring.  If you tag something as oneway=yes you must draw the way in the correct direction.  It's no use having an exactingly traced dual carriage way road with both carriages tagged oneway in the same direction.
-  If you reverse the way after adding the oneway=yes tag then don't say yes to changing it to oneway=-1 (in josm) as that's just as bad, the way will point in the wrong direction when rendered.
-  When you draw in the two fillet roads where a way joins a roundabout make it two oneway ways, not a v shaped oneway way.
-  There is no need to put a oneway=yes tag on a roundabout, it's implied by the junction=roundabout tag.


4. Inappropriate source=* tag

-  I found several ways that are tagged source=nearmap and are clearly not, likewise I found several that are clearly source=nearmap but are not tagged as such.  Nearmap has been good enough to permit the use of their imagery so make sure you tag it appropriately.
-  There's other items of this as well such as source=survey;Yahoo;Yahoo_imagery;etc....  If you upgrade the source of something to survey or nearmap then change the source tag to reflect that.


5.  Un-intentionally joining

-  When you join a way to another, make sure it's the way you really want to join it to.  For instance, a dual carriageway road with an admin boundary running down the center median strip.  A new way is added and joined on to a carriageway but because the user adding the road is not careful of where they click on the way it's added to the admin boundary and not the road, or joined to both.  If you can't see the two separate ways then zoom in closer.  Josm and potlatch will show which way you are going to join to.  If it's showing both then zoom in until you can get them separate.


6.  Intentional joining

-  Roads joined to admin boundaries or the admin boundaries tagged as roads.  Particularly in nearmap areas this is a real pain when it comes to editing anything associated with it.  The ones I did see, the admin boundary does not even line up with the road on the nearmap imagery and to change it takes a serious amount of time.  If your mapping from nearmap or survey there is no justification for using an admin boundary as a road or joining a road to it, even for one node.


7.  Abbreviations

-  Abbreviations in street names are a no no.  Read the wiki page at http://wiki.openstreetmap.org/wiki/Key:name,  DON"T do it.  At the moment in the Bunbury area alone there are 380+ abreviated street names (according to josm validator).


8.  Validator

-  USE IT.
-  If your using josm and you don't have the validator plugin loaded you're nuts, or just plain lazy.  Potlatch you need to check with keepright.  Don't just rely on memory, every time before you upload (in josm) validator will check and advise you of anything that is not quite right, fix it before uploading.  When you finish editing for the day/night/whatever run validator on the data you currently have loaded so that you can see what needs to be fixed before completing and do it then.


9.  Talk-au mail list

-  Join it.
-  I know there can be lots of garbage on here at times but It's there to pass on information to all users in Australia and those who wish to keep track of what's going on in Au mapping.


-- 
Cheers
Ross




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