OSGeo Offers Up a Tiling Specification

By Adena Schutzberg

A Specification Grows in Cyberspace
E-mail lists and blogs covered the Open Source Geospatial Foundation's (OSGeo) announcement of a Tile Map Service Specification last week. It's a vision that springs from a real world problem: Web Map Servers (specifically those that offer free/public data via the OGC's Web Map Service Specification) go down or get bogged down. That means that the Landsat data you were counting on to use as the background for a map may be slow to show up or never reach you. Schuyler Erle offered up a vision to solve this situation at the Open Source meeting in Minneapolis last year (document here).

Erle’s animated presentation (it was a lightening session) and the fact that so many in the room (myself included) had "been there" provoked a lot of response. In brief, and not too technically, he envisioned a series of servers that cached commonly used public data and could redundantly serve it up, really fast. That idea seems to have grown to include the idea of tiles and a standard way of calling those tiles. The interest from last year apparently continued to this year's FOSS4G conference held in September, resulting in, among other things, a wiki.

Some bloggers have examined practical issues - like where to store data and not pay too much. Other bloggers examined the idea in general, including our own contributing writer Simon Greener.
It is nice to see the use of tiled map libraries becoming more visible and getting some respect. Post MrSID and ECW, there was, I think, a presumption that technology like image catalogs were "old technology" and we know what such a pejorative tag being "old" is in the buzzword driven world of modern IT.

It appears that the increased visibility of Tiled Map Services, such as Google Maps, etc., has meant that the issue of image catalog use is being revisited.

About time.
OSGeo: Standards Organization?
I can't comment on the technical merits of the specification as it gets pretty deep pretty fast. But I did wonder about OSGeo's plan for its role (or non-role) in developing standards. The organization's mission does not include standards, per se: "The Open Source Geospatial Foundation, or OSGeo, is a not-for-profit organization whose mission is to support and promote the collaborative development of open geospatial technologies and data." One of the organization's goals, which underlie the mission, however is to promote standards: "To encourage the implementation of open standards and standards-based interoperability in foundation projects."

I contacted OSGeo to get a sense of its plans concerning standards. This from OSGeo President Frank Warmerdam:
This is not well understood internally yet. On the one hand, I don't want to take on a "standards process" as a part of our mission. I am generally pleased to have OGC, ISO, IETF, etc take on that role which is a hard one.

On the other hand, we have lots of folks on different projects interested in establishing some defacto common approaches, which in some cases might later be taken to a formal standards organization.

Whether we formalize this in any way is still open to debate. There are those that would like to see OSGeo as a home for lightweight standards like GeoRSS and tile spec standards.
My Take
There are a few things going on here, most of which I think are positive.
  • OSGeo brought together enough players to agree that this is a common problem.
  • OSGeo enabled members and the open source community to get together to propose a solution without any formal standards process. This is not unlike how GeoRSS got going, though it was not under any organization's (OGC, OSGeo, W3C's) auspices.
  • OSGeo has not ruled out anything at this point - OSGeo might do standards, or it might depend on existing organizations to formally vet what it produces, or neither of the above.
  • OSGeo, like GeoRSS.org, has put out a document that people can begin to explore. To date, I've found one implementation from Paul Ramsey at Refractions.
Who knows who else may try it this specification? Who knows what open source implementation might appear? Who knows if the open source community, the data community, educational institutions, state imagery server, or even the recently up- and- running Libre Map (free DRGs in one place) might give it a try?

The interest in "lightweight standards" is growing. GeoRSS is getting hot. Carl Reed wrote about microformats in OGC News (which I edit for OGC) a month ago. I read about a WFS-Basic, a trimmed down version of the OGC's Web Feature Service Implementation Specification. So, Warmerdam's suggestion that OSGeo might be part of that world makes sense.

Published Friday, November 3rd, 2006

Written by Adena Schutzberg

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