In+ersec+ion for Spatial People

Many of us probably deal with a lot of geodata that significantly evolve over time, the need for geodata versioning mechanisms is clearly a major one in many sectors. About a year ago we mentioned OpenGeo's GeoGit project, and now OpenGeo shared their vision for distributed versioning of geospatial data. This is important stuff.

In addition to this intro, here's the 3-part series:

1. Distributed Versioning for Geospatial, a new approach offers an outline of our vision of geospatial versioning
2. Distributed Versioning Implementation outlines the work we’ve already done
3. Distributed Versioning, Potential Development lays out potential plans for the future

From their introduction: "As opposed to spatial data being be locked-up in a single machine or database, we see a future where it could live in a collaborative infrastructure that can track data’s origin and evolution, much like source code. [...] A distributed version control model can better address such problems as collaborating between users or organization, maintaining authoritative data, and enabling offline, low-bandwidth, or intermittent connectivity."

You probably know what Git is, the modern distributed revision control system, replacing CVS and Subversion for many projects. Spatially Adjusted made me aware of the GeoGit approach.

Here's what the documentation written a month ago says: "Following on the core Versioning WFS work, in 2011 OpenGeo started experimenting with a new way to handle versioning, drawing on git, a distributed versioning system built for Linux and widely used. There are two different paths taken, both of which warrant further investigation:

• Using git and github directly, storing data as geojson in files
• Drawing inspiration from git core code and adapting the structures to work with geospatial information

[...] 

The code for the core repository can be found at https://github.com/opengeo/GeoGIT . This code backs both a GeoSynchronization Service module (a spec by the OGC to synchronize data) and the versioning constructs of WFS2. The plan is to eventually get both in to the standard distributions of GeoServer.

[...] 

For the geogit implementation we instead code things to be optimized for the fact that a typical geospatial representation doesn't have much nesting - it's just a bunch of features. The index is orthogonal, doesn't need to be part of the tree structure. But the problem we had when we tried to use straight git with lots of leafs is that it wouldn't really work. It doesn't scale to a single directory with millions of files."

Here's a few recent open source-related geospatial news:

• Via the OSGeo-Discuss list, I learned about pgVersion, a PostGIS versioning tool: "Versioning of Postgis-Layers will become essential, when more than one person edits the same layer concurrently. To manage concurrencing editing of a single Postgis Layer the pgVersion management system supports your work. The idea is to create a versioning system for editing PostGIS-Layers similar to source code versioning systems like CVS or Subversion."
• There's a new Python QGIS Cookbook available from Martin Dobias, named PyQGIS Cookbook
• Geomajas has graduated out of OSGeo incubation, Geomajas is an extensible open source web mapping framework in Java
• Here's a new free GeoServer 2.0 introductory workshop
• Here's an entry on editing gvSIG maps with Inkscape, on a side note, if you don't know Inkscape yet, try it, it's an excellent open source alternative to Illustrator
• The OpenGeo Suite Community Edition 2.3.0 has been released
• GeoNode is not at version 1.0 yet, but you can learn more about it with this GeoNode presentation