OSM UK's first tile layer

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OSM UK's first tile layer

RobJN
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]:<a href="http://tiles.osmuk.org/LRpolygons/{zoom}/{x}/{y}.png">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:<a href="http://inspire.landregistry.gov.uk/inspire/ows?SERVICE=WMS&amp;FORMATS=image%2Fpng&amp;LAYERS=inspire%3ACP.CadastralParcel&amp;FORMAT=image%2Fpng&amp;TRANSPARENT=true&amp;VERSION=1.1.1&amp;REQUEST=GetMap&amp;STYLES=&amp;INFO_FORMAT=application%2Fvnd.ogc.gml&amp;EXCEPTIONS=XML&amp;_OLSALT=0.789927776902914&amp;SRS={proj}&amp;BBOX={bbox}&amp;WIDTH={width}&amp;HEIGHT={height}">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

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Re: OSM UK's first tile layer

Jez Nicholson
Nice one. I've been wanting to do this for ages.

Re: file size. Can JOSM and iD display Mapbox .pbf vector tiles? These would be smaller.

On Sat, 17 Oct 2020, 00:22 Rob Nickerson, <[hidden email]> wrote:
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:

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


Best regards,
Rob
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Re: OSM UK's first tile layer

Robert Whittaker (OSM lists)
In reply to this post by RobJN
On Sat, 17 Oct 2020 at 00:22, Rob Nickerson <[hidden email]> wrote:
> 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

Excellent. Ever since the new Bing imagery landed, I've been after a
good source to align things to. I've been having to rely on my own GPS
traces and/or existing mapping so far.

By the way, when there was some previous discussion on this list about
using OS data for imagery alignment, an issue was raised about needing
to ensure any transformation from OSGB grid coordinates to WGS84 is
accurate enough:
https://lists.openstreetmap.org/pipermail/talk-gb/2020-August/025077.html
. Popular transforms may be out by a few meters (which would be
noticeable in our detailed mapping.) Are you doing such a
transformation, and are you sure what you're doing is sufficiently
accurate?

Robert.

--
Robert Whittaker

--
Robert Whittaker

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Re: OSM UK's first tile layer

ndrw6
In reply to this post by RobJN
Hi Rob,

Good stuff, it's definitely worthwhile. Thinner lines could work better
(for me 1px would be perfect), especially that the max zoom stops at 17.
You could perhaps consider increasing the max zoom a notch as well.

Are the numbers in wms tiles UPRNs? If so, you could consider displaying
them as well.

Best regards,

ndrw6

On 17/10/2020 00:20, Rob Nickerson wrote:

> 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*
>
> _______________________________________________
> Talk-GB mailing list
> [hidden email]
> https://lists.openstreetmap.org/listinfo/talk-gb

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Re: OSM UK's first tile layer

RobJN
In reply to this post by Jez Nicholson
Hi all,

To address this and some of the other questions:

>Can JOSM and iD display Mapbox .pbf vector tiles?
I don't think JOSM can which is a big shame as it would make it much easier to host these sort of layers with minimal overhead.

>ensure any transformation from OSGB grid coordinates to WGS84 is accurate enough
Yes indeed. Currently I used QGIS to transform the data for York however I see that Mapnik can do the transform itself. For a complete GB dataset I intend to download all files and bring them together to pass to Mapnik. It probably then makes sense to have Mapnik do the transform. Any details on what transformation I should be using would be much appreciated. Likewise if you know a location that gets a big error if done wrong, that would help me check.

>Thinner lines could work better
Yes, I think so too.

>consider increasing the max zoom a notch as well
Hopefully the new OSM UK board can investigate that as it will need a beefier server so would push costs up.

>Are the numbers in wms tiles UPRNs?
My understanding is that they are not. That level of coordination would be amazing but we're not there with Open Data yet!

P.S. If anyone is aware of the equivalent data for Northern Ireland, Isle of Man or the Channel Islands, please let me know.

Best regards,
Rob


On Sat, 17 Oct 2020 at 08:16, Jez Nicholson <[hidden email]> wrote:
Nice one. I've been wanting to do this for ages.

Re: file size. Can JOSM and iD display Mapbox .pbf vector tiles? These would be smaller.

On Sat, 17 Oct 2020, 00:22 Rob Nickerson, <[hidden email]> wrote:
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:

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


Best regards,
Rob
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Re: OSM UK's first tile layer

Great Britain mailing list
The Ordnance Survey provides a transformation between OSGB36 and ETRS. It is described on this page https://www.ordnancesurvey.co.uk/gps/transformation/ and on the pages linked from there. The transformation is definitive. In other words, OSGB36 is redefined as being what you get when you apply the transformation to sets of ETRS co-ordinates. This must mean that if you compare an OS 1:1250 National Grid plan, with an older version of the plan from the era of OSTN02, features may have shifted slightly.

The transformation involves a mathematical transformation, and an adjustment based on a look-up table, to make the result match the errors in the old triangulation system. The OS provides applications to do the transformation, both ways, for a range of platforms. It also provides source code, the look-up table, and details of the mathematical transformation.

JOSM handles projections using proj. If you want to know what JOSM does with EPSG:27700, you need to know how it is defined in proj. The source code of JOSM includes the OSTN02 look-up table (15MB), but it can't be in the jar (also 15MB), so I don't know how that works.

Rob asked about position errors from the Helmert transformation without a look-up table. Here are some examples.
Larger errors
Place             error, m
St Kilda           4.9
Scilly             4.7
Lizard Point       4.1
Butt of Lewis      3.2
King's Lynn        2.7
Mallaig            2.6
Flamborough Head   2.4
Colchester         2.4
Plymouth           2.4
Nottingham         2.3
Anglesey           2.1
Northampton        2.0
North Foreland     1.9
Isle of Man S      1.9
Carmarthen         1.9
Smaller errors
St Catherine's Pt  1.4
Carlisle           0.8
Edinburgh          0.6
Aberdeen           1.8
Thurso             1.6
Orkney             1.0
Foula (Shetland)   1.2
The errors are particularly small near Bristol, Edinburgh and Fair Isle. They exceed 2m in South Devon, Cornwall, East Anglia, Nottinghamshire, Lincolnshire, the East Riding of Yorkshire, Pembrokeshire, Anglesey and Western Scotland.

+1 for referencing GB to ETRS.

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