JA:Why OpenStreetMap?
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なぜOpenStreetMapを作っているのですか?
多くの国で、地図データ (ジオデータ) は無償ではありません。政府は地図データを作成、販売し、お金を稼いでいます。つまり、我々の税金は、地理データの作成コストと、地図の印刷コストの両方に使われています。米国でも、パブリックドメインのTIGERなどは存在するものの、改良して完成した地図は、著作権で保護されることが一般的です。
このような商用の地図データは、わざと「罠」（Copyright Easter Eggs）を含んでいることがあります。例えば、存在しない道や教会、学校などの偽物の情報を入れておき、データを無断利用して地図を作成した人を見つけられるようにしています。もちろん、地図データが正しくない理由としては、新たな道ができたり、単に地図を作成した人が間違えたといった場合もあります。
間違った地図データを修正するのは困難です。多くの国では、公正な使用権を少しでも超えたことをしようとすると、違法になります。道の名称を修正することも、新たなバーの情報を追加することもできません。また、コンピュータプログラムの中で地図データを用いる場合も、想像以上のお金を支払う必要があります。では、友達宛の招待状の中に地図を同封したり、掲示板に地図を貼る場合は？ 実は、このような行為も、合法とは言い切れません。
一方、安価なGPSユニットをはじめとする技術の進歩によって、我々は互いに協力しながら、上記のような制限のない、独自の地図を作ることができるようになりました。そうすることで、我々は自分たちの暮らす場所について、自分たちの手によって説明する権利を、少し取り戻すことができますね。
Google Mapsを使えばいいのでは？
短い回答: Google MapsのデータはOrdnance Surveyをはじめとする複数の組織の著作権によって保護、所有されています。Googleはそれをライセンシングしています。もしデータを使いたい場合は、お金を払う必要があります。
長い回答:
Most hackers around the world are familiar with the difference between "free" as in "free beer" and as in "free speech". Google Maps are free as in beer, not as in speech.
If your project's mapping needs can be served simply by using the Google Maps API, fine. That's not true of every project, though. We need a free dataset which will enable programmers, citizen scientists, social activists, cartographers and the like to fulfill their plans without being limited either by Google's API or by their Terms of Service. The data used in Google Maps is either owned by Google itself, or sourced from NAVTEQ and Tele Atlas, two big mapping companies. They, in turn, have obtained some of this data from national mapping agencies (such as the Ordnance Survey). Since they've made significant financial investments to gather this data, these organisations are understandably protective of their copyright.
If you collect data from Google Maps in this way, you are creating a "derived work". Any such data retains the copyright conditions of the original. In practice, this means your data is subject to the licensing fees, and contractual restrictions, of these map providers. That's exactly what OpenStreetMap is trying to avoid.
Please don't be misled by considerations of software copyright, or of Terms of Use. The Google Maps API can be incorporated into open source projects, sure. But this only governs how you use the software - it doesn't have any implications whatsoever for the data displayed by this API, which is still under copyright.
(It's not yet clear whether it's ok to create a derived work from aerial photography : some readings of UK law suggest that you can do this without 'inheriting' the copyright in the photography. A definitive ruling on this could open up new avenues for OpenStreetMap and similar projects, but in the absence of such a ruling, we're continuing with the approach of sourcing our own, 100% independent data.)
Further reading:
- Google Maps' Terms of Service. Note particularly the 'Map Information' section:
- "Geocoding data for map content in Google Local is provided under license by Navteq... and/or Tele Atlas... and subject to copyright protection and other intellectual property rights owned by or licensed to NAVTEQ, TANA and/or such other third parties."
- "Also, you may not use Google Maps in a manner which gives you or any other person access to mass downloads or bulk feeds of numerical latitude and longitude coordinates."
- The OpenStreetMap mailing list archives. You may want to search them for phrases like "derived works", and for a thread in October 2005 called "London locations".
- Can I use Google Streetview ? on help.openstreetmap.org
How can a project like this create accurate maps?
By the very nature of the wiki-style process there is no guarantee of accuracy of any kind. Then again, few proprietary maps carry a guarantee of accuracy, either. In fact, some have artificially-introduced errors.
The essence of a wiki-style process is that all users have a stake in having accurate data. If one person puts in inaccurate data, maliciously or accidentally, the other 99.9% of people can check it, fix it, or get rid of it. The vast majority of good-intentioned participants can automatically correct for the few bad apples.
As they say, though, your mileage may vary. The Wikipedia project has shown that a large amount of good quality data can be collected but it can be difficult to weed out the inevitable errors.
A full editing history is stored for each user. Since April 21, 2009, users can attach Wikipedia-like edit summaries to their edits, and there is a History tab on the main page that shows recent edits to the selected area.
At the moment the best way to answer this question is to judge for yourself. One way is to pick an area that you know well and use the OpenStreetMap viewer to see how well the map data corresponds to your own knowledge. Maybe you will see something wrong or inaccurate. More likely you will find there's nothing there yet. At this stage, our main challenge is to extend our coverage, without copying from existing maps. As on Wikipedia, it's easy to edit, so you can help!
You seem to have a lot of existing map data. Where did it come from?
Many keen contributors, and sporadic imports of data from open-licensed sources. In areas where there are no such data sources (most areas) we have to start from a blank slate, and head out there to survey the streets ourselves. Despite starting from scratch, we have achieved a good level of completion in many places.
Why is the data sometimes inconsistent?
"OpenStreetMap is a free editable map of the whole world. It is made by people like you." Which means the database will always be subject to the whims, experimentation, and mistakes of the community; this is precisely OSM's strength since, among other things, it allows our data to quickly accommodate changes in the physical world.
Who owns OpenStreetMap?
You do. The data and software is owned by you, the contributors.
There is an organisation called the OpenStreetMap Foundation which exists to protect, promote, and support the project, but does not own the data.
What does your license allow me to do with the OSM Data ?
See Legal and License for more information.