SK53 has commented on the following diary entries

Post When Comment
Mapping natural and planted habitats 13 days ago

Again can only agree. There's many a time when it's the only thing I've been able to do because image resolution not enough to pick out which parts of a woodland are conifers & which not.

Mapping natural and planted habitats 13 days ago

Dont know why I didn't comment before. I think I am very much in agreement with this. It's not just that using a multiple dimensional tagging approach helps inexperienced users, but in many cases even the most experienced user only knows "here be trees".

Other dimensions:

  • Canopy height
  • Species mix
  • Ground layer: is this a bluebell wood or a marsh
  • Field layer: is it bracken, heather, bilberry, bruchholz, brash, bramble
  • Shrub layer: does it exist, what is it composed of, density etc
  • Tree spacing
  • Dominant species (when appropriate)
  • in management: plantation (i.e. regularly spaced in rows for easier harvesting), coppicing with standards, selective removal etc
Railway Crossings challenge for MapRoulette 3 months ago

With respect to Postgis queries: gridding the data is always a good strategy for reducing in-memory processing requirements. For analysing European & US road networks I've experimented with grid sizes anywhere from 7.5 minutes to 10 degrees. I would imagine for this task you'd probably be fine with something of the order of 1 degree.

Another route for your data would have been Overpass querying for highways sharing a node with a railway. Max Erickson is usually my goto guy for how to do this kind of thing.

If you used Osmosis to populate a snapshot schema then you just need a plain SQL query on using ways, and way_nodes. You want all nodes in the way_node table which belong to at least 2 ways, something along the lines of the following (untested) (SELECT DISTINCT node_id FROM way_nodes wn JOIN ways w ON wn.way_id = WHERE (w.tags?'highway OR w.tags?'railway') GROUP BY node_id HAVING COUNT(DISTINCT way_id) > 1) and COUNT(DISTINCT COALESCE(w.tags->'highway', w.tags->'railway') > 1). I'd actually do this as separate queries to reduce the number of table scans on the big initial hit on way_nodes.

Tagged and Untagged Nodes 3 months ago

Only a million lonely nodes seems quite small by older standards. When Cadastre first came out I was cleaning up a hundred thousand or so at a time. Matt (zere) used to have a duplicated node map too which was a big problem particularly with TIGER, NHD & landuse imports in the US (more or less until ogr2osm fixed most of those isseus).

State of the Map : Some BoF sessions 3 months ago

I found it relatively easy to retrieve the significant trees in the Czech Republic, but quite a lot harder to query things related to their attributes. The SPARQL manual runs to 200 pages which is rather daunting

State of the Map : Some BoF sessions 3 months ago

I recently tried playing with the wikidata for historic/significant trees in the Czech Republic. It seems that the learning curve to get the most out of SPARQL is rather steep:

Tools I wish I had: smarter paved vs unpaved road defaults. 4 months ago

I now have fairly complete urban shapefiles derived from OSM for the whole world. I have not yet processed them to identify false positives, and in some undermapped areas some urban areas will be missing. However, I believe that a) these are more accurate than Natural Earth; b) have fewer false positives; and c) can be readily split along existing OSM boundary lines to add as a means of incorporating into a country extract. More soon/

Some comments about the OpenStreetMap Awards 4 months ago

Thanks to @imagico for discussing this topic. I had more reservations at the outset, but clearly this was an innovation which need to be tried out.

I would like to make some other suggestions for future occasions:

  • Current members of the OSMF board & the selection committee should be ineligible. This may be hard on people who have made substantial contributions to OSM as a whole, but I think it improves how the process appears.

  • Previous winners should also be ineligible. Many of the nominees were the 'usual suspects' for good and obvious reasons. However, I would like the awards to find the unsung OSM heros (of all genders). Winnowing out previous winners ought to make the field more open.

  • Regional awards. Another way to broaden the nomination pool might be to make the process 2 stage with continent-wide regional awards, with the regional winners forming the pool for the global awards. This would have two effects: decent chances of recognition in very active mapping communities without overwhelming participation from other areas; potentially more familiarity of nominees within area. I see no reason to restrict voting for regional nominees to the region which would make everything more complicated. This concept presumes a decent pool for regional nominees (easy in Europe in North America, but less easy in other regions which leads me to:

  • Nominations. Any open nomination process is always subject to a degree of bias: largely through self-selection in participation. Perhaps the role of the selection committee should be in working on creating a broader range & diversity of nominees: in particular from outside the relatively small pool of people who regular engage in the various forms of OSM communication. The committees role would then be to facilitate a broader pool of nominees: NOT to interfere otherwise with nominations. There are many members of the community whose contributions are not well-known by the broader community.

An awareness of the gifts & talents that these people bring to OpenStreetMap is only latent. Let's make them known!

The Great Canadian Mailbox Heist 4 months ago

We have had along saga about this in the UK, and we are just now beginning to lose post boxes.

Edward Betts obtained a list of post boxes from the Royal Mail back when it was a government body and subject to FOI requests. Then Matthew Somerville of OpenSociety (dracos) built a tool comparing that data to OSM. More recently Robert Whittaker created Post hoc for tracking the mapping of post boxes.

@Jedrzej Pelka : my solitary contribution to Polish post boxes!

Post box 5 months ago

Dont forget royal_cypher !

Sarah Mildred Long Bridge Closed permanently (ME/NH) 5 months ago

I walked across the next bridge seaward, the (old) Memorial Bridge almost exactly 17 years ago. A few days later crossed from MN-WA on the Stillwater Lift Bridge.

There are very few lift bridges in the UK, so have always found them rather intriguing when in North America.

Adding house numbers of one town from cadastre to OSM and survey verification 5 months ago

This sort of careful comparison of official data and what is on the ground is very useful. The fact that there are errors in the official cadastral data is not surprising (I once bought a house which had the parcel mapped incorrectly), but a good estimate of the extent of the error really helps in evaluating just how useful any given import is likely to be.

Equally really good OSM data does require revisits to check things and collect data which one has missed. This is the only way we can try to have data which is even better than the official sources.

Nottingham's Mysterious Plaster Boys & Girls 7 months ago

and I got the name from a Geograph photo by Alan Murray-Rust

Nottingham's Mysterious Plaster Boys & Girls 7 months ago

I suspect their core is rather more solid than plaster. I did document the tag on the wiki:

Don't Mention the War 8 months ago

Yes, also interesting that a house on Ribblesdale Road (Sherwood N of Valley Road) was bombed. It ought to be possible to pick it out, but many houses have been substantially extended in recent years (when I surveyed it in 2011, there seemed to be builders everywhere).

There ought to be more details of the bombing somewhere: Local Studies Library or Notts Archives perhaps. Both the Nottstalgia thread & Dominic Morrow's recent blog post about the Nottingham Canal make me intrigued about the location of air raid shelters in WWII.

One other point mentioned in one of your earlier posts was Robert Mellors : I presume this is the same person who wrote "Nottingham Suburbs Now and Then" (e.g., Basford) in the early 1900s.

Don't Mention the War 8 months ago

You're not the first to come across this phenomenon on the E side of the city: there's a new house inserted in one of the side roads in Sneinton Elements: see WWII Bombs in Nottingham.

The wikipedia has a useful map of bombed locations:

Nottingham Blitz

Trees (again) 9 months ago

I'm sure that there are fairly standard cartography symbols for recently felled woodland: usually in the form of a tree icon on its side. I've had a go at these before. but not very satisfactorily. Currently I tag these as recently_felled=yes or with year of imagery.

As BushmanK says it may be more appropriate to keep filled/unfilled symbology for deciduous/evergreen. The long discussion about 'unknown' woodland type sort of agreed for the double symbol (mixed woods would have a 50/50 split of single symbols).

Many thanks for drawing @igitov's suggestions to my notice. These do look pretty sensible. I'd probably prefer woodland over wood as the principal 'namespace').

Help map some sidewalks for cities in the U.S. 11 months ago

Hi Martijn,

sidewalk=none is the most used value when sidewalks are not present on either side of the road, not sidewalk=no. It would be nice if we avoid creating two equivalent values.


Are most subway stations actually railway=halt? 11 months ago

Places which I'd consider to be halts in Switzerland include a number of stations on the RhB. Obvious ones are:

  • Trin : unmanned, trains only stop on request. The standard station building is now a private residence.
  • Acla de Funtuana : mainly useful as it is closer to the cable car than Disentis station. Not much there from memory.
  • Celerina Staz : not much used.

These are all on single track lines, and generally the RhB always has switches & more than one track in stations: it's the single thing which ensures resilience in the system.

Other lines where stations might likely fit the UK notion of a halt are:

  • Golden Pass line
  • Line from Delemont to Le Chaux-de-Fonds
  • Numerous mountain railways (Rigi, Brienzer Rothorn, Rocher de Naye)

In the UK there are some halts in odd places:

  • Furze Platt : a single platform on a branch line with a tiny ticket office manned on weekday mornings. Otherwise no station buildings.
  • Marlow : this used to be a proper station, and although it's the terminus now has about as much infrastructure as Furze Platt + a ticket machine.

Many of the stops on the lines in Mid Wales & the Highlands of Scotland would also fit the notion of halts. As would Lakenheath which is not only a halt but has about 1-2 trains a day.

I would presume that the canonical halt was Adelstrop.

Finally, what defines a halt, typically some or all of the following:

  • Low to very low passenger volumes
  • Infrequent train services
  • Single track line
  • Absent or reduced normal station infrastructure (buildings, ticket office, waiting rooms)
  • No or very limited staffing
  • Trains only stop on demand
  • On a branch line

To which we can also add the no switches, but ultimately I think the definition of halt must reflect the fact that a halt is somewhere a passenger would expect to find none of the usual services.

As most of my examples above are probably tagged railway=station this distinction may not be that useful on OSM. I would certainly strongly advise against retagging metro stations as halts.


Showing off surface tags 11 months ago

A real quickie: you can write rules of the form surface in ('asphalt','concrete'....), easier than lots of ORs. There are probably quite a few other QGIS tips which might help.