Pacific Connection(英語)

OpenStreetMap: The Map that Anyone Can Edit

Last winter, Mikel Maron and Schuyler Erle traveled to India on behalf of OpenStreetMap, whose aim is to create a detailed online map of the world. Compared to Linux and Wikipedia―to cite two of the more accomplished Web 2.0 projects―OpenStreetMap is in its early stages. There is a lot of work to be done, and it is largely being done one mapping party at a time. A mapping party is the OpenStreetMap term for a workshop. You gather together people who know the local geography, teach them how to use a GPS, and then set them loose, often on foot or bicycle. Each GPS records a track or ⁠trace,⁠⁠ of where they’ve been and a notebook, audio recorder or camera is used to track location names and other landmarks. The tracks is uploaded to the OpenSteetMap site, which is sketched over with a drawing tool against a background that may include existing public domain maps of the area, and tagged by name and map feature―for example, a highway, road, or path. After your upload is rendered, a process done once a week, the OpenStreetMap map grows slightly more complete.

That’s what Maron and Erle were doing in India. In Delhi, they met two students from West Bengal University who planned to be at the final mapping party workshop in Calcutta. "They were going to be taking the train from Delhi to Calcutta and asked if they could bring one of the GPS units with them to record all of the stations between the two cities, as well as the train line itself," Maron recalls. "That meant they were going to have to hold the GPS unit up to the window for 16 hours to get a signal. They said they had done crazier things and would trade off every hour. So there we were in Calcutta, starting the first day of the workshop, and they came walking in directly from the train station. It was 10am and they hadn’t slept at all. They handed us the GPS, and on it, they had indeed recorded every station.⁠⁠ For the students, it was the beginning of a road well traveled: they went on to adopt OpenStreetMap as their open source project for the 2008 Google Summer of Code.

It is sometimes said that Wikipedia doesn’t work in theory, only in practice. OpenStreetMap has that same unlikely ambition. "When I first started with the project, I thought it was completely audacious," said Maron. "To produce a map of the entire world by individuals walking around with GPS units and some open source software sounded absolutely crazy, but I loved it. I thought it was either going to fail spectacularly or take over because it’s such a good idea. I think it’s the latter."

What are the chances that a group of volunteers can actually map the world one highway, street and path at a time? As with Wikipedia, OpenStreetMap is competing against better funded commercial project that have a head start. Google Earth and Google Maps, Yahoo! Maps, AOL's MapQuest are in front of OpenStreetMap in terms of technology. In parts of the United States, for example, Google Maps can show you a street map, topographical map, current traffic conditions, associated satellite imagery and even a street-level view as recorded by a car with a 360-degree camera. OpenStreetMap makes no such claim. Other maps provide turn-by-turn directions.. OpenStreetMap does not.

So where can the OpenStreetMap volunteers hope to go where no commercial mapping service has gone before? First and foremost, the map they create is in the public domain, covered by a Creative Commons license. ⁠If your project's mapping needs can be served simply by using the Google Maps API, all to the good,⁠⁠ says the OpenStreetMap FAQ. ⁠But that's not true of every project. We need a free dataset which will enable programmers, social activists, cartographers and the like to fulfill their plans without being limited either by Google's API or by their Terms of Service.⁠

But the content itself is also a factor. OpenStreetMap has the potential to map well-mapped places more thoroughly than its commercial counterparts. OpenStreetMap can map some places for the first time, or at least get this ⁠geo-data⁠⁠ into the hands of ordinary people. "With most maps, it’s only economical to collect street data because of the scale of thing―driving around with a GPS is the only way to do it," says Steve Coast, who founded the OpenStreetMap project. "Whereas with OpenStreetMap, we have cyclists, hikers, people involved in geocaching, people who want to record the location of every tree in the city. The level of detail that people are recording is incredible. Our biggest community is in Germany, and they are now collecting every building in various cities, all on a volunteer basis." Hence another Wikipedia analogy comes to mind. Just as the Web 2.0 encyclopedia covers subjects that traditional encyclopedias omit, OpenStreetMap can record landmarks that traditional cartographers ignore.

Coast is quick to admit that, as a Web 2.0 project, OpenStreetMap hasn't proved itself like Wikipedia. But he also thinks that creating an online encyclopedia was "the lowest hanging fruit." Many articles, for example, can be researched online, without stepping away from the computer. Unless you are editing from Yahoo! satellite imagery or other public domain sources, OpenStreetMap requires field work―you need to be physically present―and have a basic understanding of how to use a GPS. That requires a lot of volunteers in a lot of places. "No company is going be able to pay for people to walk every footpath in the US, but that kind of project does scale to a community," he says.

Google has also recognized this potential. In June, the company launched Google Map Maker, which opens up selected countries, many of them in the Caribbean, to user-submitted maps. Google says the project was a labor of love by some Google engineers based in Bangalore. ⁠The fundamental reasons for OpenStreetMap remain intact and if anything are now stronger,⁠⁠ responds Coast on the OpenStreetMap blog. ⁠At first glance it sounds like OpenStreetMap, until you realize that Google owns the data you give them, there’s no community and you are unlikely to see use of the data in ⁠creative, productive, or unexpected ways⁠.⁠

Coast began his career as an intern with Wolfram Research, maker of the number crunching application Mathematica. He went on to University College London, where he switched majors from computer science to physics, then dropped out to work for Credo Reference (then called Xrefer), an online reference library. It was there that he started OpenStreetMap, writing the first iteration in Java, the second in Ruby using the Ruby on Rails development environment. Most of his work is licensed under the GNU Public License, GPL. "The difficult problem was the server back end," he says. "There’s lots of database stuff to do―servicing, rendering and all of those boring things nobody wants to do. Our community is heavily skewed in the same way that Wikipedia is―we have 40,000-plus editors out there going mapping, but very few people writing code, and very few of those wanting to do the boring bits. There’s lots of cool, flashing animation associated with the maps, but making a database go in the back end is quite dull. As that was something I used to do a lot of, I got stuck doing all of it."

Coast credits San Francisco programmer Tom Carden for the design of the OpenStreetMap interface. "Mikel, Tom and I were all in a pub thinking of ways to design it, and Tom just sketched it out," Coast said. Coast implemented it, with Mikel contributing the HTML and CSS. "It pretty much looks the same today," Coast says. "The interface is supposed to be analogous to Wikipedia. There’s a view tab where you’re looking at the map, then you click to edit and to other things like traces―it's all relatively simple.⁠

From Albania to Zimbabwe―opportunities and barriers

The world is a big place and so far, OpenStreetMap aspirations are larger than the territory it has actually mapped. For example, Bangladesh, Albania, Pakistan and Vietnam are all OpenStreetMap projects, but, none have gotten very far. "Macedonia is almost a blind spot on the OSM map for now," says the project entry for that country. "This should be changed.⁠⁠ The entry suggests editing be done by the aerial images donated by Yahoo!, but notes that in only one part of the country are those images sufficiently detailed. ⁠So this is to all GPS owners in Macedonia, take your traces!"―meaning, record where you go and upload the results.

Some countries have put up legal barriers. China would seem like the OpenStreetMap project of a lifetime, but the project page warns would-be mappers that the country considers amateur mapping a threat to national security and warns visitors not to be too obvious with a GPS. Some countries aren't yet projects. If you want to map Cuba, Bolivia or Uganda or even the much tamer Liechtenstein, you are by default the project leader.

In India, Mikel Maron and Schuyler Erle held mapping parties in Pune, Mumbai, Trivandrum, Bangalore, Delhi, and Kolkata, hosted mostly by universities. "There are parts of the world with no digital mapping, and if they have paper mapping, it's out of date," says Mikel Maron. "In India, all the maps are controlled by the military and are considered military secrets. Yet especially in India with people moving from the countryside to the cities, there's a massive need for maps. This is the largest democracy in the world but in a lot of places you can’t even get a map of what voting district you are in." He says that OpenStreetMap's advantage is that, with a GPS and an understanding of OpenStreetMap editing, anyone can be a map-maker. "It’s always interesting to see what happens when you take a technology to some place where it wasn’t developed. You get to see what kinds of biases are present in the technology; what sorts of assumptions were made. In India, people navigate differently. Some roads have names but many don’t, and a lot of navigation is done by points of interest and landmarks. Those landmarks then become much more important than capturing the layout."

In the United States, the project got a running start because of the public domain TIGER map data from the U.S. Census bureau. In addition, Yahoo! donated its aerial imagery, which provides a lot of detail for the U.S. "Yahoo! gave a big boost to the project," Coast says. But even so, there are limits to what that imagery shows. A footpath in a meadow may be visible, but it disappears as soon as it re-enters the forest, and as is the case in Macedonia, the resolution may just be too low . "Most of the work is still with people mapping with a GPS. I thought it would happen by people taking a different route to work each day. Instead, it's people spending two hours mapping a matrix of, say, 10-by-10 blocks."

In urban Japan, the mapping problem is three dimensional. Consider a normal 16 story tower block, writes Tim Waters in his blog last May while he was holding a mapping party in Tokyo. A freelance geospatial developer and consultant, Waters says that a comparable building in London would probably contain offices on every floor―an easy mapping problem. But in Japan's larger cities, "such a building will have multiple uses: a lower basement containing "shops and retail units as part of the underground street, leading to subways," an upper basement that "may have restaurants and boutiques. Ground floor (1F) could be the building entrance, possibly a kiosk, and a bakery or cafe at street level. The remaining floors above ground: a university department, teaching area, library on two floors, three bars on another, restaurants on another. Offices on other floors, a nightclub on another. Space is used. But it’s vertical. Even in smaller towns with shorter buildings, multiple uses on each floor is quite comm8on. Signs outside showing what’s on each floor are provided - but it’s still a bit weird going up four stories in a lift to a pub!"

But for all its challenges, Japan is one of OpenStreetMap's biggest success stories, thanks in part to Hiroshi Miura, who launched OpenStreetMap Japan last March. Miura, who corresponded with me in English by email, first learned of the project at a Koedo Linux Users Group meeting in August 2007 from embedded Linux developer Nobuhiro Iwamatsu. "He likes bikes and is interested in GPSs, so I asked him how enjoyable OSM mapping is. He answered that riding a bike is more interesting than drawing lines on a blank screen." But Miura was interested enough to buy a Nokia E61 phone and a GPS, and to sign up. He didn't find much activity: just three people active on the OpenStreetMap wiki and no Japanese mailing list. Miura figured that the language gap was a problem, and translated the OSM wiki into Japanese, which brought attention from the ITPro news site. After more people joined, Miura became convinced the Japanese project was at a tipping point, and so he started the site. OpenStreetMap Japan in turn has attracted more people, including more who are willing to map.

Among the potential benefits for OSM in Japan, says Miura, is the ability for more people to make informed decisions on how land is developed. "Also, there are many mappers who are interested in bicycling and hiking. They are unhappy with proprietary maps that are incomplete and not up to date with the kinds of information they need.⁠⁠ OpenStreetMap, he says, transforms what might have been a regional hobby into a collective worldwide effort. Miura also sees parallels with Linux, which is especially true in Japan where most geographical data is proprietary.

In the first three months of OpenStreetMap Japan, Miura hosted three mapping parties. "The biggest one was in May, a mapping weekend in Kamakura town, which attracted 13 people, including some Linux users, a geographical researcher, and even a GPS shop owner. One of our members is a researcher in Tokyo University who studies natural environment and ecology. He and his colleagues are mapping mountain areas in a national park. He told me the work is quite valuable because proprietary maps don't show such detailed tracks." Miura knows it will take many people to map Japan's many roads. But with newer cell phones incorporating GPSs, more people will have the tools to get started right in their pocket. He sees OpenStreetMap as a central repository for data from people who don't yet know the project exists. As for his own plans, Miura sees a tie-in with his professional life, where he is helping build the open source business for system integrator NTT Data Corp. "As as I start an OSS business, I hope to eventually start an open geo business, as well. That's my dream."

Miura refers to "wikinomics," a term coined by Don Tapscott and Anthony D. Williams to describe the intersection between the "croudsourcing" represented by OpenStreetMap and the for-profit commercial ventures that rely on that data. Mikel Maron and partner Andrew Turner have launched Mapufacture, which aggregates geospatial documents from around the Web. Users can use that data to build custom maps, while developers can use an API to build custom applications. The maps can also be incorporated in other applications using the Google Earth KML format, as well as GeoRSS, a means of encoding coordinate data in RSS and Atom feeds.

For his part, Coast and business partner Nick Black launched CloudMade in 2007. The company's first two products, still in pre-alpha release, are APIs for embedding maps in Web and mobile applications. Coast views the relationship between CloudMade and OpenStreetMap as comparable to that between Red Hat and Linux. "You have a bunch of guys coding kernel drivers and interfaces, and another bunch of guys who answer the phone and install service," he says. "Similarly, we have a large community―over 42,000 people―adding map data, which is valuable, but which many people wouldn’t trust off the bat, the same way that they wouldn’t trust Linux, because they want someone to blame when it goes wrong. We provide the goods and services so that people can feel comfortable using the data."

Sidebar: From GPS to OpenStreetMap

Mikel Moran tells the story of OpenStreetMap's first tag edit war, which pitted an expatriate Brit living in Northern Cyprus against a Greek Cypriot whose father came from a village that is now in Northern Cypress. "The expat Brit was using Turkish names for Northern Cypress because that's what they are called now, and the town signs use this. The Greek Cypriot took great offense to this and changed all of the names―street names, town names―in Northern Cypress into Greek. Then the other guy changed it back. It went back and forth and back like that until one of them complained by email and I got involved in trying to negotiate a settlement. It’s silly. The database is fully localized so you can include as many names for places as you want in the local languages."

Indeed, the tagged geometry schema for OpenStreetMap is politically neutral. Maps are comprised of "data primitives," which are described by tags. A data primitive can be a one-dimensional "node"―that is, a coordinate (or, in GPS parlance, a "waypoint⁠). Two or more nodes can define a two dimensional "way." Ways are typically linear: a street, path, railroad line, or river, for example. A "closed way" is a way in which the first and last nodes meet―creating an enclosed space like a rectangle, which in turn can represent, among other features, a building, lake, forest, or golf course.

Data primitives are assigned tags which describe their properties, including the name and categories. To help keep categories uniform, the OpenStreetMap wiki lists an extensive set of "map features," including highways, waterways, railways, aerialways, amenities, sports facilities, stores, and much more. The tag can contain other attributes as well. A highway tag, for example, might contain these elements:


name=Pasadena Freeway



To refine or extend a map, you can simply pick some corner of the world and add intelligence. In an online video demo, Steve Coast does that with a random part of Bagdad, comparing the existing map with a satellite display and filling in the gaps. The other possibility is to get out in the world, record a track with a GPS, taking note of the names and notable landmarks along the way. You can upload the track and turn it into a way using OSM's online editor, called Potlatch, or work offline using the JOSM, the Java OpenStreetMap Editor. In a video demo, Coast puts JOSM through its paces by uploading a set of digital images he had snapped on a bicycle while simultaneously recording a track. By synchronizing the camera's clock with the GPS, he was able to show via a set of icons where on the track each of the digital images was taken.