Schools

In the same spirit as my earlier posts on OSM coverage of shops and healthcare facilities, I've now had a crack at estimating the number of schools that can be found on the map. I've used Department for Education figures to get an estimate of the number of schools we should find in each local authority area in England. These are pretty comprehensive. They include  independent schools as well as state funded primary and secondary schools. They also include some nursery schools (basically those receiving state funding), special schools (for children with specific educational needs) and pupil referral units (for children excluded from other schools).

By comparing these figures with the number of features in OSM that are tagged as a school I get an overall figure for coverage of schools in England around 75% - which looks pretty good. Local authorities that have particularly thorough coverage include Cambridgeshire, York, Sheffield, Hartlepool, and Bath. There's a patch around Barnsley, Doncaster, and Rotherham where coverage is low.

Some of these figures look too good to be true. I suspect that my collection of OSM features is too crude, and that this results in some double counting - perhaps as a result of the way campuses have been tagged. That's going to take a while for me to investigate, but meanwhile, this is what the first iteration looks like.

Primary healthcare

Our ability to access public services has been used as one indicator of social inclusion and quality of life.

To help with transport planning and other aspects of policy, governments have measured the ease with which we can access education, and healthcare, using public transport, walking or cycling. They also measure our ability to reach food shops, and employment. It occurred to me that it would be interesting to know how well OSM content covers similar ground.

Since policy makers see access to such facilities as being important, perhaps there are creative ways in which OSM data could be used to make it easier for people to reach key public services?

At the moment I can’t see how to replicate the official measures exactly. I can't see an easy way of measuring completeness of food shops, but I can get somewhere near by trying to measure how well all shops are covered. In healthcare I can compare lists of NHS GPs, Pharmacies, Opticians and Dentists in England with those I can find in the OSM database. I'm not sure where to find similar data for Scotland and Wales. At some point it should be possible to produce a similar measure for schools, but I haven't got round to it yet.

Breaking the lists down by local authority, I reckon that Halton, Wokingham, Cambridgeshire, Islington, and Derby score particularly well mapping local healthcare, with around half of their facilities mapped. Luton, Blackburn, and Doncaster have the most healthcare facilities to add. In those authorities I can find less than 2% of the number of facilities I expected to see in the database.

Looking at both healthcare and retail together, most places show similar levels of coverage for both. Derby and Islington seem to have particularly good coverage of retail, alongside some of the highest coverage of healthcare facilities. Other areas that rank highly on both counts include Bedford, Birmingham, Cambridgeshire, Camden, Halton, Southwark, and Wokingham.

It's worth noting that I'm using government data as a way of measuring OSM data, not the other way round, and this is not to suggest that OSM should be deliberately working towards a comprehensive directory of this stuff. It is interesting, though, to speculate what kind of new applications might start to be viable as coverage develops.

Convenience stores and supermarkets

The standard classification system for different types of business uses the concept of "Retail sale in non‑specialised stores with food, beverages or tobacco predominating". This makes two important distinctions: between non-specialised, and specialised shops (Sainsbury's vs the local butchers); and between shops that are mainly concerned with food (Waitrose) and shops concerned with other stuff (John Lewis). It still covers a wide range of different types of business - from a hypermarket to a cinema kiosk (including village stores, NAAFI shops, confectioner / tobacconists, and old-fashioned grocers).

In this context, OSM contributors make widespread use of "supermarket" and "convenience store" to describe non-specialised food shops. There are a few tagged "kiosk", "general store" (in various spellings), or "grocer" (in various spellings) but these only amount to about 2% of the total in this area. There is only a smattering where different shop types are combined in forms such as "convenience;alcohol".

The retail experts, IGD, reckon that there are 91,500 stores selling groceries in the UK, of which almost 8,000 are supermarkets (or variants), and more than 48,000 are convenience stores. About 6,500 of the convenience stores are on forecourts. Most of these will probably be marked in OSM as a petrol station, rather than a shop. That leaves nearly 42,000 convenience stores that we should be able to find. However, this might still be over-stating things a bit. The Association of Convenience Stores reckons that there are 33,500 convenience shops in the UK.

Across Great Britain I can find 5,849 supermarkets in the OSM database, and 6,928 convenience stores. So on face value, current coverage of supermarkets is about 73% and coverage of convenience stores is about 16-20% (depending on what baseline we use).

Normally a convenience store is quite a small store, with extended opening hours, while a supermarket is larger, and opening hours are more tightly controlled. In the UK, shops smaller than 280 square metres (about 3,000 sq. ft.) have greater flexibility on Sunday trading hours.

Where a shop is added to OSM with a building outline we can get a rough idea of the floor space, and we can use 3,000 square feet as as way of distinguishing convenience stores and supermarkets. There's no point in being rigid about this, but in general a "supermarket" with a floor space of less than 3,000 square feet is probably a convenience store, and a "convenience store" with floor space of much more than 3,000 square feet is probably a supermarket.

Where I can measure them, the average floor space (actually building footprint) of a convenience store in the OSM database is 2,000 square feet, and the average floor space of a supermarket is 43,000 sq feet. Both are well inside the right range. However, about 4% of features tagged "supermarket" could be in the wrong category, and about 20% of features tagged "convenience store" could be in the wrong category (though most of these are still quite small). Re-allocating these according to size rather than tagging would take supermarket coverage up to almost 90%, and convenience store coverage down to around 14-17%.

The bottom line is that coverage of supermarkets looks pretty thorough - the majority are in the database, they can easily be identified, and tagging is pretty consistent. Coverage of convenience stores is better than for most types of shop, but could be more thorough. Many can easily be identified in the database, but some of those might better be tagged as "supermarket".

According to the Department for Transport, most of us are within 10 minutes of our nearest food store, and within reasonable travelling distance of 3 or 4. The chances are that at least one of these is in the OSM database, and at least one is still waiting to be added. The missing ones are likely to be some friendly local convenience store - not some massive supermarket chain. Which hardly seems fair.

The lost shoppers

Today's retail trading statements make gloomy reading. Shops had a slow autumn, followed by heavy discounting over Christmas, and face various other pressures. I thought it might be timely to look further at OSM coverage of the retail sector to see how things were going from a different perspective.

So far, I reckon that about 10% of shops in the UK have been added to OSM, but it's a bit of a mixed picture.

The coverage varies by type of shop. Post Offices and Cycle shops seem to be well covered (I reckon that about half of each are in the database). Garden Centres, Clothes shops and Computer shops are covered better than most types of shop (around 20% of each have been included). Butchers and Off-licences are close to the average (at around 10%). However I can only find a small proportion of the expected number of Flower shops, Furniture shops, Fishmongers, Greengrocers and Hardware shops. On face value the coverage of supermarkets is particularly good, but these are difficult to classify accurately so these figures are a bit iffy. Given the public spirit that drives a lot of OSM activity I was slightly surprised to see that coverage of charity shops is quite low (6% or so).

There are regional variations. I reckon the most densely mapped areas have recorded around half of the shops on the high street, while the less well covered have recorded only one shop in a hundred. These rankings for shops follow a different pattern to the rankings of road coverage. For example, Derby and Islington are doing particularly well recording shops. Although Islington also comes fairly close to 100% in the ITO comparison with Ordnance Survey road data, Derby comes further down the same rankings.  Wolverhampton does pretty well on both rankings, while Wigan scores well on streets, but near the middle on shops.

(with apologies to various rural counties, there was an error in the previous version of this map, which this one seems to fix)

To produce the map I extracted OSM data related to shops, and allocated each within the relevant local authority boundary. For comparison I use National Statistics on the distribution of retail units by local authority. This only covers VAT and PAYE registered businesses, so it will understate the actual numbers of shop units in each authority. Hence the raw percentages will be over-stated. However, it should be a good enough proxy to compare geographic distributions. To measure the proportion of each different type of shop recorded in OSM I used estimates of the actual number based on a mix of public domain data from National Statistics, Valuation Office data drawn from business rates, and figures from various trade bodies, and industry analysts.

Embedding a map

Dara Ó Briain, no less, asked this on Twitter today "Does anyone know how to grab a portion of a map from google map, say, to include in a document?".

That was 11 hours ago, so he has probably had loads of answers by now. If not, here is how I would do it...

• Go to Open Street Map. 
• Zoom and slide the slippy map to the area you need. 
• Hit the "Export" tab.
• Choose the format you want (it's probably going to be Mapnik for a document, or embeddable HTML for a web page).
• Choose the option you want (its probably going to be PNG or JPEG to embed in a a document. If you don't know which of these you want then it probably doesn't matter, so use the default. Use PDF if you want to email something that people can easily print).
• Hit the Export button.

I claim my free puppy.

First ride of the year

On the way I passed this milepost, which tells travellers how far they have to go to get from A to B. It's a kind of 19th century GPS I suppose - but I wouldn't want to carry one of these around with me.

I didn't do anything as exciting as travelling all the way from A to B today though. I just did a short, fairly hilly loop of a few miles.

In 1901 Charles Harper described this section of road as "a weariness and an infliction to the cyclist, for it goes on in a heavy three miles' continuous rise". I cunningly rode it in the opposite direction, so at this stage I was on a steady descent. I'd done the climbing earlier though, so I feel that I had paid my dues.

Ten bike rides that I won't be doing in 2012

What with one thing and another I didn't get out on the bike as much as I would have liked in 2011. I've resolved that this year will be different, but one has to draw the line somewhere.

1. I believe the views at Alpe d'Huez are impressive, but it does look a bit crinkly. 
2. I haven't got the right bike to participate in the Brompton World Championships
3. It's one thing not to wear special clothes for cycling, but another to wear none at all. For the sake of spectators I've decided that I should give the London Naked Bike Ride a miss again this year.
4. There are still a few days left to apply for the Fred Whitton Challenge, but I understand they are normally over-subscribed, so I ought to give somebody more deserving the chance to pick up the gauntlet. 
5. Six months to cycle round the world? That's far more time than I can spare.
6. The Tweed Run promises a metropolitan bicycle ride with a bit of style. I don't qualify. Not even a bit.
7. There are good reasons why they invented the safety bicycle, and I wouldn't be joining the Knutsford Great Race, even if it was on this year.
8. I'll pass on this one as well. I don't know where it is, but it lies well outside my comfort zone.
9. I don't own any lycra. Just one reason for ruling out the Giro D'Italia 
10. We now have enough space (and enough weather) for a virtual reality trainer, but I reckon that I've already spent far too much of my life sitting inside staring at a computer screen

And that's about it. There are a few rides left to chose from. Some of them might be a bit of a challenge, but mostly I suspect that I'm just going to be pootling around slowly, exploring the local area and enjoying myself for another year. And there's nothing wrong with that.