The Open Geospatial Consortium and EarthCube
An EarthCube Technology Paper
Prepared by David Maidment1, Ben Domenico2, Alastair Gemmell3, Kerstin Lehnert4,David Tarboton5 and Ilya Zaslavsky6
OGC Document 11-159
18 October 2011
Introduction
EarthCube aims to create an integrated system to access, analyze and share information that isused by the entire geosciences community. The Open Geospatial Consortium (OGC) is anorganization of which more than four hundred companies and agencies are members, whose
purpose is to create open source standards for sharing geospatial and observational information.
The authors of this paper are users of OGC standards in our work in hydrology, meteorology,
climatology, oceanography and in the solid earth sciences, in other words, in key disciplinary
fields that contribute to the Geosciences. Moreover, the OGC has an effective process forengaging individuals from many countries in standards development and interoperability testingthat encourages them to set aside the roles they play in their home organizations and instead
focus just on what is needed to share a particular class of information across the globe. This
paper examines the hypothesis that an OGC-like process could be useful for broader sharing of
information in the geosciences.
OGC Information Standards
The OGC has developed standards for sharing geospatial and observational information as webservices. A web service is a function that enables one computer to make requests to anothercomputer in a structured way and to receive appropriately coded responses in return. Sharing
geoscience information requires the capacity to publish, catalog, discover, access and process
information located on computers at any geographic location. OGC geospatial information
service standards include:••••

Web Map Service – for communicating georeferenced images;
Web Feature Service – for communicating geospatial features as points, lines or areas
with attached tabular attributes, that is, discrete spatial objects;
Web Coverage Service – for communicating continuous spatial fields asmultidimensional arrays.
Web Processing Service – for executing functions or models on remote computers

The OGC information framework for observational data is founded on an observations andmeasurements model that has four key components – a feature of interest has properties that areobserved by a process that produces a result. This model originated in the solid earth sciences	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	   	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  	  1	  Center	  for	  Research	  in	  Water	  Resources,	  University	  of	  Texas	  at	  Austin	  	  Unidata	  Program	  Center,	  Universities	  Corporation	  for	  Atmospheric	  Research,	  Boulder,	  Colorado	  3	  Environmental	  Systems	  Science	  Centre,	  University	  of	  Reading,	  United	  Kingdom	  4	  Lamont-­‐Doherty	  Earth	  Observatory,	  Columbia	  University,	  New	  York	  5	  Utah	  Water	  Research	  Laboratory,	  Utah	  State	  University,	  Logan,	  Utah	  6	  San	  Diego	  Supercomputer	  Center,	  University	  of	  California,	  San	  Diego	  2

OGC	  11-­‐159	  The	  Open	  Geospatial	  Consortium	  and	  EarthCube	  where it is used to describe properties of geological units (features of interest) via sampling
features such as transects, wells, or specimens, but it has been generalized into the fluid domains
where the feature of interest is understood to be a fluid domain in the vicinity of an observation
instrument whose properties are being measured by that instrument. Sensor Web Enablement isa set of OGC specifications that define information encoding and service interfaces forinteracting with a network of sensors through internet, and within this there is a Sensor
Observation Service that describes how to query and obtain information from a particular
instrument.
An organization may provide access to a large number of web services, and to index them, OGC
has developed a Catalog Services for the Web, which provides a single end-point web address
through which the underlying services can be individually discovered and accessed, rather likegoing to the card catalog when entering a library in the traditional style.
Services in Solid Earth Science
Geospatially referenced data in the Solid Earth Science are characterized by their highly diverse
nature, ranging from large-volume sensor-based time series measurements to small but highly
diverse and unstructured data generated ‘manually’ by investigators in the field or ex-situ in thelab. The integration of these heterogeneous data types is critical for many of the large scientificquestions and challenges in the Solid Earth Sciences. Major NSF-funded science initiatives suchas Ridge2000, GeoPrisms, and the Critical Zone Observatories require integration of multidisciplinary datasets. OGC Web Map Service and Web Feature Service providers havesuccessfully been deployed by major Solid Earth Science data centers such as UNAVCO, IRIS,
the Marine Geoscience Data System, the National Geophysical Data Center, and EarthChem toadvance the integrated discovery and (Figure 1).

Figure 1. WMS and WFS features and layers include GPS campaign surveys and continuous stations,seismic stations, earthquake locations, seafloor bathymetry, expedition tracks.

A higher level of interoperability and data integration in the Solid Earth Sciences can beachieved by applying the OGC Observation & Measurements (O&M) model to encode different
types of observational data. White papers submitted by Rick Hooper and Ilya Zaslavsky
emphasize that the OGC O&M model can provide a common basic encoding for both sensor2	  	  OGC	  11-­‐159	  The	  Open	  Geospatial	  Consortium	  and	  EarthCube	  based and sample-based observational data. Several O&M profiling efforts are emerging in theSolid Earth Sciences (EarthChemXML, SoilML) and will complement existing standards such as
WaterML 2.0 for hydrologic data and the Climate Science Modeling Language (CSML) for
atmospheric and oceanographic data.
Services in Atmospheric Science
Standards play a key role in allowing the Unidata Program Center to make data available to othercommunities without diluting the support provided to the core community of researchers andeducators in the atmospheric sciences. While it is not practical for the Unidata Program Centerto support the specialized analysis and display tools of other disciplines, it is important to makethe datasets available via standard protocols so users from these other disciplines can continue tomake use of their own tailored analysis and display tools with data available from Unidata.
Standards are also enabling Unidata to work with others who provide complementary functions.
Web Processing Services are emerging as a key element in distributed systems that enable moreanalysis and display functions to be performed on the server side. This has several advantages,
for example, in the era of "big data," the processing can be done where the data reside. It also
makes it feasible to initiate and control sophisticated interactive data analysis and processing
from more modest mobile platforms. To gain a sense of power afforded by incorporatingweather data into analyses done using tools from the GIS community, Figure 2 shows
demographic information as an overlay on real-time, high resolution, local forecast models being
run in regions of high precipitation probability. The weather data is conveyed in netCDF(network Common Data Form) via the OGC Web	  Coverage	  Service protocol. NetCDF is the firstbinary encoding format standard of the OGC.

Figure 2. ArcMap Rendering of Schools and Hospitals in a Region of High Precipitation
Services in Ocean Science
Over the last five to ten years in the ocean sciences there has been an increasingly strong
adoption of OGC standards, and related applications and projects. Many of these have employed
the OGC Web Map Service standard and used it for serving gridded ocean model and satellite3	  	  OGC	  11-­‐159	  The	  Open	  Geospatial	  Consortium	  and	  EarthCube	  derived data products. Examples of such projects and applications include the Integrated Ocean
Observing System – OpenIOOS, MyOcean (which employs the University of Reading’s ncWMS
software), IMOS – the Australian Integrated Marine Observing System and the SeaDataNet
project. More recently there has been an upsurge in the use of other OGC web service standards,including extensive use of the the OGC Sensor Web suite of standards, especially the Sensor
Observation service (SOS). This is becoming the preferred way of serving in situ data streams inthe marine community, as opposed to the Web Feature Service which is not as well suited tohandling time series data. This is partly because the Web Feature Service standard is designed toserve features as a whole, and sub-setting is a common requirement in this type of service.
Projects and initiatives which have incorporated the use of the SOS standard include OOSTethys,
OpenIOOS and the OGC Oceans Science Interoperability Experiment.
Figure 3 shows a Web Processing Service by which the difference between two sea surface
temperature grids is computed – the request for the computation is initiated at the University ofReading, the calculation is done with the grids in netCDF format at the British Atmospheric Data
Center, and the result is delivered back to the University of Reading as a Web Map Service.

Figure 3. Sea Surface Temperatures – a Web Processing Service delivers a Web Map Service
Services in Hydrologic Science
Hydrologic science relies on data from multiple sources and advancing understanding inhydrology requires combining information from multiple lines of inquiry. Figure 4 (a) shows ahydrologic scientist accessing information from GIS, modeling, observations, weather andclimate modeling and remote sensing. Observations data measured at point locations areparticularly important for hydrologic science, such as streamflow and rainfall gages, waterquality sampling points, and groundwater wells. Some of this information is obtained from
intensely measured small watersheds, including the Critical Zone Observatories, but synoptic
scale studies of the nation or large regions rely very largely on observations made by water
agencies of federal, state and local government.
4	  	  OGC	  11-­‐159	  The	  Open	  Geospatial	  Consortium	  and	  EarthCube	  The Consortium of Universities for the Advancement of Hydrologic Science, Inc (CUAHSI) has
invented a language, WaterML, for the communication of water observations data as a web
service, and the US Geological Survey and some other water agencies have adopted WaterMLand now publish their real-time and historical time series information in this format. CUAHSI
has indexed water observations information at about 2.3 million locations in the US (Figure4(b)), and provided access to this information in WaterML. Beginning in 2008, CUAHSI has
been working with the OGC to modify WaterML, and a revised version, WaterML2, is being
considered for adoption by the OGC as a profile or specialized version of the OGC Observations
and Measurements specification, and thus as an international standard for encoding waterobservations data.

Figure 4. CUAHSI Hydrologic Information System
Geoscience Information Services
Any information system that emerges from EarthCube will build on the information
infrastructure that NSF presently supports in the Geosciences. This includes several longestablished data centers, such as the Unidata in Boulder and the IRIS Center in Seattle, and somenewer initiatives including the CUAHSI Hydrologic Information System program and theIntegrated Earth Data Applications at the Lamont-Doherty Earth Observatory. Each of these
activities focuses on the needs of a particular domain geoscience community and because
domain sciences tend to view the same physical circumstances in different ways, and even using
different language, it is likely that there will always be the need for variations in terminology for
different domain communities. This is similar to the task that the OGC deals with indeveloping international standards in the face of different languages of the countries its members
represent. At its core, however, information about the earth rests upon a physical model of theshape of the earth and of the evolution through time of the phenomena that take place on andwithin the surface of the earth, its atmosphere and oceans. This suggests that it is possible todevelop a common set of Geoscience Information Services that the domain science communities
could share.
In geoscience cyberinfrastructure projects, reliance on service-oriented architecture (SOA) is
now a common approach to organizing distributed nodes of information. While the variety ofproblems and research designs in the “earth science fabric” leads to increased complexity ofscientific data types and respective services, standardizing on a limited set of information models
and services, adopting them as community standards and making the services available via
representative hubs would help resolve a range of common challenges in the earth sciences.
These include discovery and interpretation of data from neighboring disciplines; added5	  	  OGC	  11-­‐159	  The	  Open	  Geospatial	  Consortium	  and	  EarthCube	  confidence in data that have complete standards-compliant metadata, including QA/QC
information (which is critical for establishing trust in such a diverse data-rich environment);
ability to access data from anywhere in the system via common interfaces and bring them into
applications that each discipline is familiar with. This vision, however, requires that the certain
nodes in the EarthCube system (information hubs) are developed to support easy translation
between disciplines. They would include services for translating structure, syntax and semantics
between information models, services and vocabularies adopted by different domains, and would
publish metadata catalogs that can be federated with metadata catalogs in other domains, for a
one-stop data discovery and interpretation. In addition to “semantic web” elements, thesetranslations will be helped by scientists themselves who will be able to connect and explain theirdata via social networks. EarthCube is first and foremost about connecting people.
OGC Process
The OGC has two component programs, a Standards program and an Interoperability program,which develop standards and test them in practical situations. Standards development occurs bytaking existing standards and developing more extensive specifications, or profiles, that serve
particular purposes. Interoperability testing is carried out by interoperability experiments, pilot
studies and testbeds, that represent successively increasing degrees of commitment andinvolvement by the participant organizations in testing proposed standards. Domain working
groups for particular disciplines focus activity in specialized areas of interest. The momentumof this activity is maintained by Technical Committee meetings that are held each three months
at some location in the world, where standards are adopted and information exchanged in person
among groups that otherwise communicate electronically.
Conclusions
The geosciences community embraces both the solid earth and fluid earth sciences and considers
observed and modeled information distributed over the globe. Web services provide amechanism for one computer to request information from another in a structured way for avariety of information types. The Open Geospatial Consortium is an international standards
organization for developing web services for geospatial and observational information, including
standards for cataloging and processing that information, and has recently joined with the World
Meteorological Organization to jointly develop standards for information in hydrology,meteorology, climatology and oceanography. OGC standards are already fairly widely used in
the NSF geosciences community. All these things suggest that EarthCube should seriously
consider as one option for its development an OGC-based services-oriented architecture for thegeosciences.
Should NSF decide to proceed in that direction, this could involve the formation of domain
working groups within individual geoscience disciplines, the formation of a TechnicalCommittee for the Geoscience Information Services that considers common information
standards across the geosciences, regular meetings each three months of the TechnicalCommittee at NSF data centers around the United States, the advancement of web services
standards in areas where current standards are deficient, and the testing of services provision
through pilot studies where formal testing of the effectiveness of delivery of information isundertaken.
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