Due to some complications with my salary, I had to head on down to the Inland Revenue Enquiries centre in Cambridge.

I initially Googled it - it turned out that the OSM namefinder knew where it was if I just typed "Inland Revenue, Cambridge". Even with all the time I spend on it, I'm often pleasantly surprised by just how much OSM "knows".

Whilst I was down there, I took the opportunity to map some features on Brooklands Avenue. I also improved the road / car park data for the Eastbrook (Government offices) site and the Cambridge University Press site. I traced the outline of the Government offices from satellite view. It's on the Osmarender layer now; needs a little clean up but i think it's useful detail to have.

Interesting fact:

Not many people realise that Cambridge, UK has a nuclear bunker. Not just any nuclear bunker - one designed to support a regional government for the East of England during a nuclear way. It even has a BBC studio for making broadcasts from.

http://www.bbc.co.uk/cambridgeshire/features/2003/10/cambridge_nuclear_bunker.shtml
http://www.subbrit.org.uk/rsg/sites/c/cambridge/index.html

I knew the bunker was somewhere off Brooklands Avenue but have previously had no luck figuring out *where*. Before going to the tax office, I took another look at the above articles and noticed that the bunker was at the back of a Government offices site - ah ha. I debated over whether to ask the tax advisor about it; he might think I was mad. When I eventually asked him (after sorting my PAYE!) he became quite animated told me something interesting - apparently there is a nuclear bunker on site and it has recently been sold. There had been a For Sale sign out on the road. Must have made for an interesting Estate Agent listing...

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Had an odd experience last week. Was out mapping a bridleway with my usual exploring buddy. It was quite late at night / early in the morning and pretty quiet. There was no moon but we were well illuminated by our bicycle lights. Late night is often a nice time to ramble through the bridleways in the cool and quiet, without running into anybody else.

We followed the bridleway signs up to a farm. The path had led us to a smart wooden gate that looked like it opened into somebody's garden - we decided not to go through there for reasons of politeness and that the sensible thing was to continue round the track at the edge of the field; with British rights of way this is almost always the right approach and you find another signpost shortly after. The route markers often assume a certain degree of ESP like that.

We carried on round the field and the track seemed to take us into the farmyard / farm shop area. There was a clearly marked "Way out" sign, suggesting this area was open to the public and we decided it would be best to just head through that in order to get back on the road, whilst keeping an eye out for any more bridleway signs. Plenty of local bridleways do go down farm access roads in order to get to the fields, so this would not be an unusual situation.

At that point a chap with a shotgun stepped out of a doorway and demanded to know what we were doing there... Ooops! I guess that wasn't part of the bridleway after all! We weren't thrilled by the presence of the shotgun (note to readers outside the UK: it's very rare to see a gun around these parts, especially in the hands of a civilian!) but it seemed to be there mainly for show and he kept it lowered at all times. He did mention that he'd considered letting the dogs out (!) but had decided they'd make too much noise (?). Again, that comment may well have been for show. Apparently they'd had some problems with theft.

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Spent a while (much more time than I intended!) tonight doing mapping around Cheltenham and Tewkesbury - the area in which I grew up!

I'm in Cambridge right now so I've been using a combination of the existing OSM coverage, NPE, Yahoo (the satellite imagery is of a very low resolution so it's not as helpful as I usually find it) and - to a large extent - my local knowledge from growing up there and from my later visits to see my parents. I've been able to add a load of POIs in the village of Prestbury. There are a fair number of new (since NPE) streets missing for this village and the Yahoo coverage isn't good enough to trace them. I'll have to take the GPS some time when I visit!

I've also added some place names and pubs between Bishop's Cleeve and Tewkesbury. I hope to be able to do a bit of more detailed mapping next time I'm in the area but I doubt I'll be able to do a huge amount. Makes a change to be working in another area, though.

I was in London yesterday for a few hours, meeting some friends. I managed to place a few bus stops (on Westminster Bridge and on Whitehall, though my coverage of these is neither pinpoint accurate nor comprehensive), a zebra crossing near Embankment and a couple of telephone boxes near County Hall).

A shame I couldn't do more but I didn't want to hold up the large group of non-mappers I was with ;-) At least I found out that it was quite practical to carry a GPS and camera with me and gather some odd bits of data when I'm in an unfamiliar city and busy with other things. I wasn't able to do a huge amount but I was still able to help a bit!

Have been continuing to trace in buildings, paths, drainage, trees from a combination of the Yahoo satellite view, local knowledge and observations from previous GPS-ing trips. I've been tagging bus stops (and on the occasions when they're missing, Post Offices and Post Boxes) and also telephone boxes (although I don't think these currently appear on any renderings, which is a shame). I've also tried to put in some farm / field boundaries I knew about where possible.

Despite Cambridge's amazingly detailed state (thanks to others - particularly David Earl) there's still plenty of useful information I can contribute, even on the fully streetmapped sections. So anybody who's looking for some mapping but thinks there's nothing to do in their local area - look again. There's *always* something you can add, either using local knowledge, GPS, NPE or Yahoo!

I'm continuing to improve the high zoom coverage of Cambridge by adding more paths within colleges, some areas of trees, drainage ditches that connect to the river Cam, etc. I've also started filling in bus stops, which are one of the few advantages Google Maps coverage has over OSM for Cambridge. I'm surveying the bus stops in person, with GPS unit and camera.

I've also traced a load more buildings on Sidgwick Site (off West Road) and in the centre (mainly churches) using Yahoo coverage, although I've not filled in the names for most of the new ones yet. I'll have to go there in person to flesh out the remaining details...

Went out with my usual expeditioning buddy and took some traces of more footpaths West of Cambridge. This time primarily between Long Road and Hardwick (finishing off a network of paths that were mostly already completed there) and between Hardwick and Caldecote (also joining up with existing paths).

Whilst out there I also did some detective work: the out-of-copyright NPE maps show a stream that starts somewhere near Hardwick and goes down through Coton. I've surveyed portions of this stream directly where it went alongside footpaths and was able to use the NPE map to join these portions up. Similarly, NPE revealed that a stream I'd seen flowing from Dry Drayton to Hardwick was called "Callow Brook" and extended south into Hardwick itself...

My theory is that these are the same waterway and that the old OS surveyors just didn't have time to confirm that they joined up. I'm not able to check using satellite maps as there's no Yahoo coverage in the area. I was able to extend the path of the stream a bit more through direct survey; next time I'm hoping to take some compass bearings of whatever bits I can get to, in order to confirm that they join up. It's fun to explore :-)

Today myself and my usual expedition buddy went to map the path from Dry Drayton to Lolworth and the path from Lolworth to Childerley. In the process, we discovered that Childerley is not a real village despite being mentioned on multiple footpath and byway signs in the area. It doesn't exist...

Now, there's Childerley Gate near the A428, which does indeed exist. But the Childerley pointed to by the footpath / byway signs does not exist. Interesting. There's a huge farm there and plenty of public footpaths passing through. There is also a small collection of houses around a central street that look suspiciously like a village but apparently aren't. There's no right of way to Childerley Gate from here but a farmer kindly gave us permission to use their private access road to the south (presumably this used to be a public road to the village), which we used to bail out of the area and back onto normal roads.

NPE Map has a fix on where Childerley "should" be ( http://www.npemap.org.uk/tiles/map.html#535,261,1 ). The legend "CHILDERLEY" presumably marks the old Parish of Childerley. Childerley Hall seems to have turned into the modern farm, although it's possible the original building lurks in somewhere. The farm's private access road appears to be the original public road into the village / settlement. The was even the little row of houses next to it, adjacent to the farm, presumably the original residences.

A little Googling found some records about Childerley, which seems to have existed until some time in the 20th Century: (http://www.genuki.org.uk/big/eng/CAM/Childerley/, http://www.cambridgeshirehistory.com/cambridgeshire/TownsandVillages/Childerley/index.html, http://en.wikipedia.org/wiki/Childerley). At some time since then, the village seems to have ceased to exist as a settlement and has become part of a large private estate - albeit with many public rights of way running through it.

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I've been confined at home by work and the weather, so haven't been able to map bridleways for a few days.

Instead, I spent some time today filling in features that are mostly visible at higher zooms - some drainage ditches near footways, the bridges in St John's College, some larger buildings on West and Grange Roads and within Churchill College. This is all from personal knowledge but after 8 years here my knowledge is pretty good!

A question: some Cambridge buildings have been drawn out as an area and tagged but also contain a lone node in their centre with the same tags. This causes Osmarender to render the details twice, although Mapnik seems to handle it better... Is this necessary anymore, or should the node tags for buildings be removed in the cases where an area for that building bears the same tags?

Since many universities (in the UK, at least) have a collegiate system, I also wondered if it would be worth having specific tags to identify individual college's lands as well as general university property.

These are pretty stunning: http://news.bbc.co.uk/1/hi/technology/7539529.stm

That said, it would also be awesome to see a rendering of the movements of OSM mappers (as derived from uploaded GPS traces) plotted on a world map :-) I wonder how many people you'd see active at once - surely the activity much be fairly constant these days!

http://en.wikipedia.org/wiki/Photogrammetry

Photogrammetry refers, essentially, to measuring stuff using photographs. It's been used in traditional surveying for years (here's a paper from 1925-1926 on the subject http://www.iop.org/EJ/abstract/1475-4878/27/2/301). There seems to be a fair bit of commercial photogrammetry software out there. The main open source software I found was Ossim (pronounced Awesome!) (http://www.ossim.org) and it does seem to be designed with surveying in mind although I'm not quite clear what its capabilities are.

I've recently noted that there's a proposed building attribute (osm.wiki/index.php/Building_attributes) for height (amongst other interesting things). Measuring a building's height isn't easy to do accurately with a GPS (firstly because elevations don't seem to be very accurate on a basic GPS and secondly because you can't always get onto the roof!). Most of use don't carry a theodolite (http://en.wikipedia.org/wiki/Theodolite) to measure this sort of thing - even if we did, they're a bit unwieldy to tote around on a bike!

I've been pondering how feasible it might be to estimate approximate building heights using geotagged photographs and a much simpler piece of software. You would need (for a simple setup):
1) a reasonably level surface, lets assume you can be roughly at the building's ground level
2) photographs from a couple of different distances - at known positions, provided by the GPS
3) the position of the building, either by walking up to the building with your GPS or by looking it up on a satellite map (or OSM itself!)

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After an evening's debugging code and munching pizza in the lab (took a while to get here, I'm starting to wonder if I should hand out OSM maps of West Cambridge to the pizza delivery guys) I thought I'd go out for a ride whilst the pile of Dominos settled in my stomach.

I walk out of the department, notice that it's much colder than the recent weather had led me to expect and then spend a few minutes fiddling with my front light bracket, putting it on upside down, losing the nut, then getting confused about which way is clockwise... By this time I'm feeling the cold a little and am glad to set off and start making some heat. As I cruised off down the cycle path to Coton, I noticed things were a little dark - the recent new moon had escaped my attention and outside the twin beams of my headlight the pathway is pitch black. A section of the tarmac overhung with trees gives the eerie impression of a long dark tunnel.

Arriving at the start of the bridleway network near Coton, I pedal down to the first bend in the path, calling out to warn occasional rabbits out of my way. I reach my intended destination - the entrance to a local conservation walk - and lock up my bike, leaving the lights on low to help my find it in the dark. With the flashlight in one hand and my GPS unit in the other I push through the squeaking gate and into the field beyond. In proper English countryside fashion, the signpost had indicated the intuitive direction "up and to your right a bit". I cast about in the field looking for some kind of clue as to the path I am intended to join, walk into a spooky little wood, decide that wasn't the best plan and finally set off across the field in the direction I suspect was intended.

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I guess this is my first diary post :-) I've only just discovered this thing is here but it's a jolly good idea.

I've been making an effort to try to fill in the bridleways and footpaths around Cambridge and have been successfully finding and mapping lots of ways which don't currently have OSM coverage. I'm mapping all over the place but my end goal is to be able to declare individual areas of countryside (as defined by the roads surrounding them) "complete", having surveyed the roads all around for path entrances and followed all those paths and all their branches.

This is progressing pretty well, particularly for the squares defined by:
1) Madingley Road, Grantchester Road, New Road, Long Road
2) A428, Long Road, Barton Road, Main Street

Area 1) is the one I've thusfar located the most paths through. These paths go around (and through!) the Barton Road Firing Range site and form a pretty nice network North of Barton village. I believe I've almost explored all the branches of these paths although there may be some more waiting to surprise me.

I'll try and post back with occasional updates about where I've been.