OGC Newsletter - January 2007
CTO'S MESSAGE OGC standards and the Geospatial Web Carl Reed, Chief Technology Officer, Open Geospatial Consortium, Inc. I recently read a number of blog entries about the role of OGC standards in the evolution of the Geospatial Web. A number of bloggers suggest that many OGC standards are neither required nor relevant for use in the Geospatial Web. Other bloggers believe that OGC standards have a central role in providing the interoperability foundation of the Geospatial Web.
My view is more centrist. The Geospatial Web has been evolving since the mid 1990's when the first mapping applications, such as MapQuest and Xerox ParcMap, were deployed. During the last few years, various applications, such as emergency services, spatial data infrastructures, and consumer mapping have accelerated the growth and evolution of the Geospatial Web. During this same time period, an increasing number of applications have implemented and use a variety of geospatial standards. Some of these standards are OGC standards but others are from the Open Mobile Alliance (OMA), from ISO, from the IEEE, or from the Internet Engineering Task Force (IETF).
The reason for this is that the Geospatial Web consists of many layers. The following is a somewhat simplistic view of the number of layers that define the geospatial web. Models for defining the layers of an IT infrastructure are typically 5 to 7 layers deep.
There is the "deep" layer that deals with location as an integral component of the Internet infrastructure. An example of this is the Internet RFC (request for comment) for location enabled DHCP. (Dynamic Host Configuration Protocol Option for Coordinate-based Location Configuration Information (RFC 3825). Then there is the Link Layer Discovery Protocol-Media Endpoint Discover, or LLDP-MED, which is an enhancement to the Link Layer Discovery Protocol (LLDP) and is designed to allow for things such as device location discovery to allow creation of location databases and, in the case of VoIP, E911 services. These standards tend to be lightweight and relatively simple and very well structured semantically. These characteristics are driven by the fact that bandwidth and packet size are significant constraints. The OGC collaborates with the IETF to insure consistency in how location is expressed at this level.
Then there is the middle layer of standards that provide "gateway" access between the deep layer and the application layer. This middle layer is where standards such as OMA's Mobile Location Platform API and a variety of OGC standards, such as WMS, WFS and WCS are implemented. It should be noted that MLP uses an application schema of GML to express geometry and CRS. Standards in this layer tend to be non-trivial. A high degree of geospatial semantic richness, expressiveness and robustness is required at this layer. There are many reasons for this, such as the requirement for more precisely expressing the vast range of properties related to location, such as time, coordinate reference systems, topology, complex geometry, measurements, and metadata.
Finally, there is the application layer. The application layer is interesting in that the standards that exist at this level can be quite simple, such as GeoRSS, or quite sophisticated and semantically expressive, such as the OGC Styled Layer Descriptor standard. As with the other layers, there are other geospatial standards being developed for this level that are not OGC standards. For example the presence architecture developed in the IETF Instant Messaging and Presence Protocol (IMPP) working group has defined a format for presence information called Presence Information Data Format (PIDF). PIDF is an XML format that provides presence information about a "presentity". An extension to PIDF has been defined with a Presence based Geopriv Location Object Format (PIDF-LO). PIDF-LO carries either civic, geospatial location information or both. PIDF-LO is a GML application schema. As such, PIDF-LO itself is a relatively simple standard but one that is grounded in a very rich and expressive standard – GML. And GML is grounded in the ISO Feature model. So, in the application layer, a common characteristic is that relatively simple standards can be developed and deployed that are profiles or application schemas of other, more "complex" standards such as GML.
Location content is being created and utilized at many levels in the internet/web infrastructure. Much of this content is not being created by the GIS community! Consider DSRC [http://en.wikipedia.org/wiki/DSRC]: a short to medium range (1000 meters) communications service that supports both public safety and private operations in roadside-to-vehicle and vehicle-to-vehicle communication environments. DSRC is really about developing and deploying an extensive roadside sensor and communication network. This network will generate billions of location messages on a daily basis – and is being done entirely outside the traditional geospatial domain. And this application area will be an integral component of the Geospatial Web.
OGC standards play an important role in all levels. This does not mean that the OGC is developing standards for all levels and all application areas. Instead, many other standards organizations, such as the IETF, IEEE, OMA, and OASIS are building on the work of the OGC to define profiles and application schemas for their specific requirements. Many of these profiles and schemas, such as those used in GeoRSS and IEEE 1451, are simple and lightweight. Each meets a specific requirement.
The Geospatial Web is not just a bunch of mash-ups or even the hundreds of SDI's that have been successfully deployed. The Geospatial Web is about the complete integration and use of location at all levels of the internet and the web. This integration will often be invisible to the user. But at the end of the day, the ubiquitous permeation of location into the infrastructure of the internet and the web is being built on standards. And the work of the OGC is a principal source and foundation of much of the standards work for the Geospatial Web.
REPORT ON THE DECEMBER 2007 TECHNICAL COMMITTEE AND PLANNING COMMITEE MEETINGS IN SAN DIEGO
The work of the OGC members attending the 59th OGC Technical Committee meetings, hosted by BAE Systems in San Diego during the week of December 11th, 2006, resulted in the following key motions and recommendations:
- 06173r2 "Geographic information - Rights expression language for geographic information"
- 06-080 "GML 3.1.1 Application schema for Earth Observation products" for the use of GML Observations
- 06-141r2 "Ordering Services for Earth Observation Products"
The following documents were approved for release as OGC Best Practices:
- 06-095 "Web Notification Service (WNS) Candidate Implementation Specification"
- 06-142 "GML PIDF-LO Geometry Shape Application Schema for use in the IETF"
The following recommendations were also approved by the members:
- A revision of the OGC URN namespace identifier (NID) specification will be submitted to the IETF for formal IANA approval.
- Approval of a modification of the OGC standards approval process that will reduce the overall approval process timeline by at least 60 days.
- The candidate specification "Observations and Measurements" was approved for a formal 30 day public comment period.
- The issue of consistent use of Axis order in OGC standards was discussed at length. The members agreed that a formal statement on this topic is to be drafted and used in all OGC specifications as best practices guidance. This is a go forward statement and is not intended to require existing implementations of any OGC standards to be changed.
- ebRIM was approved as the preferred meta-model for future OGC CS-W Catalogue Application Profiles. All existing CSW application profiles will remain valid and supported into the future.
- The Planning Committee strongly endorsed the proposal by Google to bring KML into the OGC standards process. The first step will be to perform limited harmonization with OGC and ISO standards and then produce a document for consideration by the OGC members for release as OGC Best Practices. There will also be a public discussion list created so that the OGC KML related work will remain open and transparent.
The OGC Architecture Board also had its first face to face meeting. The primary discussion topics were the use of ebRIM, the relationship of Sensor Observation Service and Web Feature Service, and the role of application profiles in WFS.
Carl Reed, Chief Technology Officer,
Open Geospatial Consortium, Inc.
NEWS AND OPINION FROM THE BLOGOSPHERE
Fertile discussions of OGC specifications continue in the blogosphere (the world of blogs). Much of the recent discussion is about "neogeo" or "Mass Market Geo". Here are a few December posts:
"In this respect the attendance of the senior Google Geo staff in the form of John Hanke, Michael Jones and Brian McClendon was very important. Indeed Jones was interested in seeing how OGC could aid the standardisation of KML and clarify its relationship with GML - note these are early days but at least the right people are beginning to talk. …OGC has played a very important role is developing the 'professional' GI market. Its expertise would also have massive value to the mainstream -- important progress then!"
You can also read this e-consultancy interview with Ed Parsons for Ed's thoughts upon his departure from the Ordnance Survey. Much of what he says is relevant to the comments you are reading here in "News and Opinion from the Blogosphere."
Jo Walsh, in a December 14 Mapping Hacks entry
titled, "At the back of the 'mass market' bus", says she "…spent some time over the last month or so attempting to engage with the WFS Simple public development process marshalled by our friend Raj Singh. I backed away from it a couple of weeks ago, and wrote down at the time some of the reasons why… "
In a well-worth-reading 1400 words she says a lot about the technical and institutional difficulties and possibilities, concluding that, "I know that what I want for Simple probably falls between two stools - not expressive and flexible enough for the hardcore - not familiar and straightforward enough for the much larger neogeo constituency. Right now the process risks failing both communities and emphasising the difference between them, and that's an awful shame."
Sean Gilles, writing about "OGC and the Geo-Web" at Import cartography blog – Python, Geospatial, News and Opinion on December 17, said, "I'm pretty sure Raj Singh... gets this already, but one of the things the OGC needs to understand before it can help to geo-enable the Web is that there's more to ubiquity than just dumbing down specifications to the grade level of the mass market. Systems with simple rules allow the evolution of complex and surprising features. Our teeming, expanding, World Wide Web was made possible by its deliberately simple design.
"W*S protocols have opened minds and hinted at possibilities, but are not engendering a geo-web. Pictures and data flow dutifully through channels, but there is no evolution of linkage, no complex, organic patterns or structures, no sum that is bigger than its parts. There's no web here."
Also on December 14, Jeff Thurston wrote in his Vector One blog, after reading the posts mentioned above, "I think many people are trying to adapt, to adjust, to transition and change - toward the next plateau, the next direction, the next need.
...The continuum runs from simplicity to complexity. From local to enterprise. From closed to open. Different things will appear along the continuum, dependent on needs and requirements.
I think the so called "traditional" side of the equation is a savvy and smart bunch. I think the "non-traditional" are similarly so.
What is important to me may not be important to you, but it does not de-value what I think or need.
We need to get this part right. So what's the conduit to make that happen?
Then the sky is the limit."
And here's a set of comments from Tom Kralidis, on a range of topics, posted December 29 on his "Tommy's Scratchpad" blog:
"GeoRSS is here: GeoRSS made v1 this year at foss4g2006 and has proven to be a simple, yet very effective way to tag feeds. I've used and integrated in all my projects (I use the GML flavour) which produce RSS content by way of outputting an overview map based on the position. It gives the developers endless possibilities, and folks just love to see 'where' a post is. ….
MapServer SOS support: It's great to see OGC SensorWeb support in MapServer. Given that MapServer can already do stuff like spatial, temporal and aspatial queries, I think SOS was a relatively easy initial implementation effort...."
There's more from Tom at his blog, on the ResEau portal launch, MapServer committer access, ebRIM, OWSContext progress and MapServer Brazi.
Torsten Becker, who implemented a GeoRSS Viewer at http://ExploreOurPla.net, is also engaged in Climate Change work. He points us to the “Onearth: WMS Global Mosaic,” a valuable source of daily weather-related satellite images at NASA’s JPL Laboratory.
Every day two snapshots of most populated places on Earth are converted into a datasource for a WMS server. The daily snapshots are of data collected by the Moderate Resolution Imaging Spectroradiometers (MODIS) flown on two NASA satellites, TERRA and AQUA. There are three styles for each sattelite, visual, 721 pseudocolor and NDVI. A resolution of about 250m/pixel clearly shows hurricanes, floods, wildfires, ice shelves and other phenomena that have a bearing on Climate Change. An archive gives access to all pictures from yesterday back to December 25, 2004.
Composite of data collected January 19, 2007 by MODIS/Terra. Updated daily.
Another dataset from this site is the WMS Global Mosaic, a high resolution global image mosaic of the earth. It was produced from more than 8200 individual Landsat7 scenes. Each scene requires more than 500MB of storage. These images have been collected during 1999-2003. The highest resolution image has a ground relative resolution of 15 meters, or 50 feet. The mosaic contains all nine spectral bands of the Landsat7 ETM+ instrument. Access to the data is provided through an application that implements the OpenGeospatial Web Map Server Specification, band combinations can be generated using the OpenGeospatial Style Layer Descriptor mechanism.
Clicking on an image or on a caption on this site takes the user to an interactive WMS map browser that requires no software download. The browser has limited capabilities and is intended only to provide a functional view of the capabilities of the map server itself. In the browse mode, you can click on the image to recenter the view or use the zoom bar at the top of the image to zoom. The distance left or right of the black/blue center marker controls the zoom in or out amount, up to four times the current level. The browser will let you zoom out more than a single earth width, which will generate an error, and zoom in past the level of detail of the data. Other WMS clients, such as worldKit, WorldWind or Punt can be used to view the data. Users of WorldWind or Punt should use the OnEarth.xml configuration file. Save a copy of the configuration file in the WorldWind/Config/Earth subdirectory, and use the layer manager to enable layers from this server. Four different styles of the WMS Global Mosaic are configured, together with the daily TERRA/AQUA MODIS mosaics.
The WorldWind config file contains four representations for the WMS Global Mosaic and the 6 daily MODIS composites. The same data are usable by Google Earth via KML files already configured to use WMS for most of these sets. The page containing the Google Earth links is at http://onearth.jpl.nasa.gov/KML.html. The OGC WMS specification makes the data compatible with major earth viewers like Google Maps, FlashEarth and ExploreOurPla.net, and with other applications including ESRI software, TopoFusion, and GlobalMapper
An FGDC metadata compliant record is available at the site. The base dataset can be downloaded, and a mirror download site is available at Telascience. The Web Map Service (WMS) server providing access to the WMS Global Mosaic and other datasets is accessed via this base URL. An XML encapsulated document describing the datasets and the server are can be retrieved via a Capabilities Request
This project involves a large commitment of time. Lucian [dot] Plesea [at] jpl [dot] nasa [dot] gov (Lucian Plesea) is the one who maintains it. As Torsten says, “I think this public project is the most valuable ever which implements the OGC WMS specification and supports time access via the TIME parameter. With any viewer capable of building WMS urls it is possible for anyone to have a close look at our planet and to conceive its delicate state.”
The OnEarth WMS server itself has no current support, and in danger of being closed due to lack of funding. The MODIS WMS composites themselves have been the result of voluntary work.
Know of a website that uses OpenGIS specifications to solve a real world problem or demonstrates an interesting use? Or of a website that enhances the use and understanding of OGC's work? Drop the lmckee [at] opengeospatial [dot] org (editor) an e-mail with the details including the URL, organization behind the website, specifications used, technology used and the goal of the website.
OGC welcomes new members who joined us recently.
SRS Technologies, Inc. (U.S.)
Technische Universitat Berlin (Germany)
University of California, Los Angeles-Center for Embedded Networked Sensing (U.S.)
OGC IN THE NEWS
- OGC in the Press
Pact aims to spark real-time 2-D/3-D Web visualization
December 28, 2006
Podcast: 2006 Year End Editors’ Round Table
December 22, 2006
1Spatial Addresses Hot Topic of Spatial Data Management
December 4 - 8, 2006
Innovative Ways to Improve Digital Geospatial Data Infrastructure Sought
December 4, 2006
NASA WorldWind-based browser for large volume image data leverages OpenGIS web map service
Watershed Modelling in Kentucky
Gary R. Harp
Creating a Satellite-data Integration System
The Importance of International Standards
Rong Xie and Ryosuke Shibasaki, Center for Spatial Information Science, University of Tokyo, Japan
The Emerging Geospatial Semantic Web
December 2006 - OGC Press Releases OGC Demos Results of OGC Web Services Test Bed
December 21, 2006
OGC Announces Invitation to Qualify for Interoperability Program “IP Team”
December 20, 2006
OGC Members Adopt OWS Common 1.1 Specification
December 20, 2006
OGC(R) and Web3D Consortium Agree to Advance Joint Standards
December 19, 2006
OGC Announces Geospatial Linking Service Interoperability Experiment
December 14, 2006
OGC and TDWG Biodiversity Information Standards will Collaborate
December 14, 2006
January 22-25, 2006
Map World Forum
January 22-25, 2006
(Discount for OGC members, see brochure)
January 25, 2006
Best practice makes perfect with Open Geospatial Standards
March 1-2, 2007
Winston-Salem, North Carolina, US
2007 North Carolina GIS Conference
March 21-23, 2007
Washington, DC, US.
ETS - IV: Convergence: CAD / GIS / 3D / BIM
April 16-20, 206
OGC Technical and Planning Committee Meetings
July 9-12, 2006
OGC Technical and Planning Committee Meetings
For further info on events please contact gbuehler [at] opengeospatial [dot] org (Greg Buehler).
Please send comments and suggestions to:
lmckee [at] opengeospatial [dot] org (Lance McKee)
Acting Editor, OGC News
Open Geospatial Consortium, Inc.
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Copyright 2007 by the Open Geospatial Consortium, Inc.