Monthly Archives: December 2009

David and Josh on Video

We had a busy autumn at conferences. Josh Marcus represented us at the first International Crisis Mapping Conference in Cleveland, Ohio.  He presented our work with HunchLab, the crime analysis, early warning and forecasting system we have been developing with support from the National Science Foundation.

Over the past year, David Zwarg has been devoting his 10% research time to supporting the mapping components on the SourceMap project at the MIT Media Lab.  He had a chance to present at the Boston Ignite Spatial a couple of weeks ago.  Check out his presentation on this video.

OpenStreetMap License is Changing

OpenStreetMap: the free wiki world map

Whether for commercial software or open source projects, the crafting of a license is one of the most important decisions a company or team can make.  The license determines who can use the software, how it can be used as well as how it can be shared.  Open data projects, while different from open source software, face the same types of questions.

OpenStreetMap is probably the single largest and most significant open data project in the geospatial realm.  The project was started because “most maps you think of as free actually have legal or technical restrictions on their use, holding back people from using them in creative, productive, or unexpected ways.” Up until now, OSM has been using a license called Creative Commons Attribution Share Alike (CC-BY-SA).  However, OpenStreetMap is more like a database than it is like a text document or photograph and database projects have run into some specific problems with the CC family of licenses.  The OpenStreetMap project is proposing a move to the Open Database License (ODbL).  Like many collaborative projects, the move is being made by submitting the change and the justification for it to the community for review, comment and vote.

Why make this move?  What’s wrong with the CCBYSA license? A lot of people use the CC licenses to publish their articles, photos, paintings and other creative work.  But the various forms of the Creative Commons licenses are designed to work within the legal infrastructure the surrounds the concept of copyright.  Structured databases are collections of facts.  When factual data (like streets drawn on a map) are arranged the way you’d expect it to be, it’s not necessarily protected by copyright law, particularly under U.S. copyright law, which only protects works that arise from creativity.  If copyright doesn’t apply to factual data and the CC licenses are based on copyright law, we have a problem.  The is the core of the issue.  Even the Creative Commons folks have said that the CCBYSA license should not be applied to databases.

The new proposal, ODbL, resolves the issues by applying copyright where it applies and applying contract law where it does not.  It attempts to take the best of both worlds and create a happy medium that applies to database projects like OSM. As perhaps the largest open database in the world, OSM was one of the touchstone cases that the Open Data Commons and Open Knowledge Foundation used to build the license.

But it’s also interesting to note what it won’t cover.  The ODbL will only apply to distribution of the OSM database.  Contributions to OSM (like GPX tracks and other database edits) are covered by a Contributor Agreement which will refer to the ODbL as the means of distributing their contributions.  It won’t cover image tiles generated based on the OSM database.  It won’t cover the OSM wiki, which, since it is text and therefore considered a creative work, will remain covered by CCBYSA.  And it won’t cover the software source code used to run the entire OSM system – that will be usually, but not always, be covered by the GPL.

There remains some controversy within the OSM community. Many members, including one of the founders advocating for the change, feel that a completely free, Public Domain license (no limits on usage) would be preferable.  The ODbL will retain the “share-alike” concept of the current CCBYSA license (requiring both attribution and that changes be submitted back to the community and distribution carry the same terms). They feel that the spirit of reciprocity codified in this approach is stronger. The new OSM license will include both the concept of attribution and share-alike because many members of the community feel that this limitation benefits the project.  Nonetheless, others feel strongly that a truly public domain situation would be better in the long run, encouraging broad usage without consideration for consequences.  In the best democratic tradition, however, both sides express their positions in Vote Yes and Vote No pages.  Check them out.  And if you are an active member of the OSM Foundation, make sure you cast your vote.

You may be tempted to file this under “boring”, but the nuances of licenses are an important part of the creative economy in which we operate.  They set the terms under which we interact with each others work.

A Myriad of Projections

One of the facets of our work that makes it different from other software development is the need to deal with geographic projections and coordinate systems. Projection systems are the mechanisms by which we spread a semi-spherical Earth onto a flat surface. Google, Microsoft, Yahoo and ESRI use global coordinate system called Web Mercator for their online systems. Here in Philadelphia, the local municipalities use the NAD 1983, State Plane, South Pennsylvania coordinate system with a Lambert Conformal Conic projection. While satellites and improved measurements have changed and improved our coordinate systems as well as given us a few new ones, we have not actually seen that many new projections in recent years.

But now there’s not just a new projection but a whole family of new ones based on an alogorithmic approach developed by Jack van Wijk, a Netherlands computer scientist at the Eindhoven University of Technology. This news is actually almost two years ago, but Dr. Wijk was recently awarded the Henry Johns award by the British Cartographic Society, so it was back in the news.


Projections are always about trying to square a circle but failing – none of them can get it right, and they all distort, only varying in terms of the type and degree of distortion. The Mercator projection, for example, preserves shape but sacrifices an accurate size of those shapes, while the Peters projection preserves size while sacrificing shape.

Dr. van Wijk’s new projections are called Myriahedral, representing projections that cut the globe into a polyhedron composed of large numbers of facets. The development is significant because it manages to reduce the angular demormation (shape) by preserving area as well, essentially squaring the circle.  It represents a whole new class of projections because, depending on the parameters, the result will change with many maps being possible.  By allocating the most weight to land masses, a map is generated that lines up the continents.  By shifting the weight to the oceans, the algorithm produces a single giant sea surrounded by land.

Read the original article: The Cartographic Journal, DOI: 10.1179/000870408×276594

Walkshed NYC Enters NYC Big Apps Contest

We’ve been wrapped up in walkability to bring you Walkshed NYC. Using 10 data collections drawn from the NYC.gov Data Mine, we’ve entered Walkshed into the NYC BigApps competition to provide custom walkability mapping to NYC residents.

Just how much customization?   Sixty billion custom walkability maps for each NYC resident — yes, we said each resident.    Walkshed NYC contains 17 preferences each of which can be set to 11 values—that’s 505,447,028,499,293,771 possible maps that you can select from. Plenty of possibilities for all 8,363,710 NYC residents.

The complexity only begins there. Each of the 17 walkability preferences are made up of 157,715,256 values arranged in a grid to cover the city. The values in your selected preferences need to be combined on the fly to generate your distinct map.    Thank goodness we have DecisionTree to power this immense calculation.

But measuring a city’s walkability is just the beginning.  Planning water resources, land use, better sidewalk networks and bike lanes, and distane from diverse habitats are just a few of the ways that geographic technology can help make our towns and citoes operate in a more sustainable manner.  Also have an obsession with walkability or sustainability?  We need your support and votes.  Voting runs from December 15th – January 7th.

On
December 15th , vote to put walkability on the map.

Explore Walkshed New York