[Talk-GB] OSM UK's first tile layer

[Rob Nickerson]

Hi all,

Just in time for the AGM, I have just published OSM UK's first tile layer.
No don't get too excited it is not a full map render. Instead I have
produced a very simple tiling of the Land Registry polygon data now that
this is under the OGL Open Data Licence. My view is that this is a good
layer to align our mapping too - i.e. when tracing from imagery we should
first align the imagery to the Land Registry polygon layer before tracing
from the imagery.

The tile URL for JOSM is:
tms[13,17]:http://tiles.osmuk.org/LRpolygons/{zoom}/{x}/{y}.png

And for now this is *York only* as an example.

Feedback that I would appreciate:

   - Is this worthwhile?
   - Do you agree that it makes sense for us to all try to align our
   mapping to this (i.e. apply imagery offsets to align imagery to this before
   tracing)?
   - The style is very simple with just a 4 pixel red line. Is this
   sufficient? What changes can be made?
   - Any tips on how to keep the PNG file sizes as small as possible? For
   now I am using the Mapnik rule "png8:c=2:t=1:m=o". Is there anything that
   can yield smaller file sizes?
   - What max zoom is worthwhile? Currently it goes to 17, is this enough?

Our plan would be to pre-render all the tiles and host them on our site.
The data doesn't change much so we would only re-render on request or once
a year. My estimate is that we'd need 35GB for tiles to zoom level 17, and
133 GB to get everything to zoom 18. Our current server is on the small
side with just 512MB memory and a 100GB disk allowance. It is unsuitable
for on the fly rendering and we'd need more disk space to get the level 18
zoom. A beefier server is of course possible but any bump in specs comes
with an equal bump in costs so worth checking this is worthwhile before
proceeding.

P.S. The Land Registry themselves host this data on a WMS service rather
than a TMS (tile) service. This makes it possible to zoom much further in.
If you want to have a look at that detail you can use their website or
(temporarily) use the following URL in JOSM. Please don't use this for
mapping as we don't have permission to use their WMS service

wms:
http://inspire.landregistry.gov.uk/inspire/ows?SERVICE=WMS&FORMATS=image%2Fpng&LAYERS=inspire%3ACP.CadastralParcel&FORMAT=image%2Fpng&TRANSPARENT=true&VERSION=1.1.1&REQUEST=GetMap&STYLES=&INFO_FORMAT=application%2Fvnd.ogc.gml&EXCEPTIONS=XML&_OLSALT=0.789927776902914&SRS={proj}&BBOX={bbox}&WIDTH={width}&HEIGHT={height}

Best regards,
*Rob*
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.openstreetmap.org/pipermail/talk-gb/attachments/20201017/4fb182a5/attachment-0001.htm>