[Talk-GB] Sorting out layering in East Anglia, Essex, London and Kent

Peter Miller peter.miller at itoworld.com
Tue Apr 19 14:31:36 BST 2011


Andy Allan just asked me a question privately about changes I have made to
layers in Wandsworth which has prompted me to do a post here saying what I
have been up in order to rationalise use of the layers in East Anglia,
London and now Kent.

The ITO Map 'Layers' view highlighted a huge amount of weird layer tags in
the area. London seemed to be particularly bad. There were parks at layer-5
and lakes at layer 1; railways at layer=1 or -1 even though they were on the
ground. I have been my way south and west from Norfolk though Suffolk and
Essex and now London and Kent sorting issues out as I find them. In the
process I have added probably 100 bridges in order to gets rivers and
railways to work properly. You can see the current view here:
http://www.itoworld.com/product/data/ito_map/main?view=22&bbox=-45397.555877915,6692718.780745626,35709.774820957,6725408.451752373&layers=&base_style=&clear_map_history=true

There is still plenty wrong as far as I am concerned, but it is getting
there. There are two underground lines which cross at the same level to the
south of Regents Park and also at Bond Street Tube. The Railway engineering
layer shows up a bunch of additional issues. Railways crossing at the same
layer without a bridge close to Crofton Park and again just North of New
Cross.
http://www.itoworld.com/product/data/ito_map/main?view=55&bbox=-6970.6313936487495,6706135.318464111,-1901.42322496925,6708178.42290209&layers=&base_style=&clear_map_history=true

I have also done an edit pass on the 'key:layer' wiki page in order to make
the rules clearer without changing the rules.
http://wiki.openstreetmap.org/wiki/Key:layer

The only extra rule I introduced was that power lines were assumed to float
about everything else and didn't need layers unless they crossed each other,
in which case one can choose appropriate layers for those sections of line.
This seemed to make more sense that guessing at a level which is what people
have been doing from time to time. Setting all power lines to 'layer=5' is
abritrary and will cause difficulties if it crosses above another line. As
such the approach seemed to be more suitable. Here is the current layer wiki
page which is written very much as a set of rules for someone wanting to
understand how to use them.

Here is the old version of the key:layer wiki page that I started with. It
has the same message as the current page (I hope), but it is much harder to
follow.
http://wiki.openstreetmap.org/w/index.php?title=Key:layer&oldid=590097


Regards,



Peter
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