LondonFreeMap
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This project now has its own home: http://uo.space.frot.org/freemap/
We're making free-of-copyright street level maps of London, starting in the East End and working outwards. We plan to rapidly develop evocative prototypes, working through Steps 1-3 below, and repeating, working outwards.
This effort is in collaboration with Openstreetmap who've been working on a similar plan for a few months, and with whom we hope to share data, hosting and algorithms, and keep the design language-neutral. To get involved, please join the mailing list .
On GIS Day, Nov 17th 2004 we're giving a short talk about Our Plan at dorkbotlondon - see FreeMapsAtDorkbot.
[edit] Our Plan
[edit] Step 1 - Collect GPS data
This part is both easy and hard. We walk, or cycle, the streets of London, with GPS units, recording our traces and waypointing useful and easily identifiable points.
>> Walk, cycle, skate? The tracklogs in the 'skate' directory at http://loaclhost.telent.net/gps/ are/will be the result of skating and/or marshalling on the various street skates that happen in London. If you can use this stuff, please feel free. If you can't use them as they stand, but can suggest alterations to the format (as long as they don't involve slowing down) to make them useful, again, please do. Let me know when you have somewhere central to upload this stuff.
> yes! skate too... this looks great, please keep the data coming!
We're building a simple web-based interface where people can upload GPS tracks and points in GPX format, a simple and common XML format. We have two GPS units to lend, and are looking for resources to acquire more.
Any kind of previously collected GPS traces - netstumblers, geocachers? - are of use and interest to us. If you can offer these, we'll provide an upload facility.
There is a window of opportunity several times a day - currently around 7-9pm and 4-6am - when there are 3 satellites directly overhead, thus accuracy is better and it is possible at all to trace areas with tall buildings and/or narrow streets. The calendar server we were using is currently down; we'll build our own if necessary.
Raw GPX tracks will probably be stored on a shared WebDAV server, perhaps hosted at UCL, for anyone to grab and re-process.
We'll store the collected points and segments in a simple PostGIS database.
[edit] Step 2 - Normalise and Synthesise Data into Real Shapes
This is the hard part, code-wise. We start with a big collections of points, which belong to arbitrary segments. We'll write algorithms which decide when several very close lines are actually the same line and thus need to be averaged together. We'll write algorithms which decide where intersecting lines are junctions, and the street needs to be split up into segments. We'll decide when small gaps in lines probably indicate a path running between them. We'll have techniques for turning collections of lines into polygons - which describe parks, or squares, for example.
Technically, this will involve a lot of hard thought and frequent mistakes in a quiet room.
[edit] Step 3 - Annotate Shapes with Real-World Semantics
This is the demanding part, effort-wise: Ground Truthing and improving on raw street data. Streets and street segments need to be labelled with their names; some of this will be possible online, from local Knowledge or by cross-referencing with old maps.
Some street semantics are crucial for navigation: e.g., "This road can be driven along but not walked", "This path can be walked but not driven along", "This road is one-way in a north-to-south direction along this segment", "This road is a major artery or a minor road".
An ideal goal is to label street segments with street numbers, so we can do proper free address geolocation. It may be possible to conduct a "civic survey", offering explanatory leaflets to homeowners in exchange for divulging their postcode.
To complete this long task properly, we need a portable annotation device, ideally with wireless connectivity. We no longer need to be going out with a GPS at this stage. An assortment of iPaqs which we can lend to trusted collaborators would be perfect.
We'll use UMN Mapserver to build a first-cut annotation interface on top of PostGIS.
[edit] Step 4a - Annotate Completed Map with Civic and Historic Information
We're looking for interested parties with deep local knowledge and existential committment. Prime candidates in the East End are the East London Postcard group, who are taking historical/contemporary comparative photographs, and are interested in doing online maps of walks to accompany their own publications.
Annotations don't need to be contained in our own repository; they can live at another specialised service, like the Open Guide To London , that we can talk to.
There are old maps, out of copyright, in circulation. Some are very high detail, but a lot of East London has changed beyond recognition since they were made. Still, they are of essential social interest and value.
[edit] Step 4b - Find Partner Organisations to Contribute to, and Back, the Project
London Green Map have a great collection of data, mostly points, describing green spaces and sustainable public resources like recycling stations, which is crying out for open publishing and inclusion in a London Free Map. We need to get to the stage where we have a plausible local prototype before starting to negotiate with them.
Local authority Planning and Building, and Street Management, departments have a lot to gain from a collaboratively built and maintained, free of copyright, body of geographic data describing their locality. It may be possible to suggest a joint application for an Open Source GIS project with Hackney and/or Tower Hamlets in the future.
[edit] Step 5 - Give Everything Away
Shapefiles, GML over Web Feature Service, RDF - any format we can think of or that people ask for export in. In addition to a Mapserver based web representation which people can call on as a base layer in their own sites and overlay points on top of. All the software we develop for London Free Map will be freely available under the GPL. We'll hopefully use Here Be Dragons as a 'geodata portal' for giving things away.
Any thought on what the license will be? Presumably, some sort of Creative Commons or similar?
