Hare, Trent (US Geological Survey (USGS)) - Co-Chair,
Malapert, Jean-Christophe (CNES) - Co-Chair
The objective of the Planetary DWG is to identify requirements to revise or extend OGC standards for celestial bodies other than the Earth. These bodies can be planets, satellites, asteroids, Sun and comets.
The overall mission is to ensure that the OGC standards remain current and relevant with the scientific requirements for celestial bodies established by the planetary science community.
All bodies that are not spatially resolved to have a disk or surface are out of scope (exoplanet, …)
Planetary bodies are mainly studied via direct optical and spectral observations of their surface. Analysis of planetary surfaces can provide key information on the evolution of the surface over geological time, the internal dynamics of planetary bodies, and/or the climatic evolution for bodies with an atmosphere. Planetary surfaces record many of the key stages in the evolution of our Solar System. To enable effective study of planetary surfaces, there is a need to combine all the available data by geographical area. These data can be from the same mission, but taken at different times, or data from different instruments across different missions. The data need to be co-registered and georeferenced to make effective and efficient analysis whatever the spatial scale (global to local). Practitioners in the field generally use Geographic Information Systems (GIS) or other spatially aware software to combine the data, visualize it and launch analyses exploiting the spatial attributes of the data. Planetary data are obtained from data repositories that are scattered around the world and usually hosted by Space Agencies and/or mission teams. There is consequently a need for interoperability between these different archives.
The use of OGC mapping standards in a planetary science context poses a number of problems related to the historic development and use of OGC standards primarily for Earth observation, as outlined below.
· Problem 1: identifiers and definition of celestial body data projections
Combining data from different data repositories requires defining a common coordinate reference system (CRS) that is understood by all. Currently, the OGC Web Mapping and Coverage standards support projection of data based on an Earth centric spatial reference system (e.g., EPSG:xxxx codes as defined by The International Association of Oil & Gas Producers).
Every 3 years, the IAU WG Cartographic Coordinates & Rotational Elements publishes a report updating the spatial reference systems for planets, satellites, asteroids, and comets (Archinal et al., 2018). The identifiers of celestial bodies will have to be versioned and uploaded to a registry visible by everyone.
In order to fully take into account the characteristics of the IAU coordinate reference system (CRS), the WKT-CRS standard must be updated.
Then, to ensure the continuity of the data update process of the WG IAU in the OGC standard WKT-CRS, a solution must be found to automate the interface between the IAU and the OGC WKT format, and possibly the OGC Definitions Server.
· Problem 2: updates of OGC standards
All OGC standards depending on the WKT-CRS standard must be updated to take into account the revised WKT standard. This DWG will verify that there is no other restriction(s) that would prevent the use of new IAU identifiers. In addition to the IAU identifiers, this DWG will work on ontologies to improve the knowledge model of the planetary sciences. For this, it will synchronize with the Geosemantics DWG and GeoSPARWL.SWG
· Problem 3: In-situ data visualization
More and more in-situ data are being acquired by rovers. The most natural way to visualize and analyze rover image data is via a "map street view" or in virtual reality. In the case of virtual reality, it is essential to ensure that the user has a minimum of 90 FPS (frames per second) in each eye to avoid motion sickness or dizziness. This means optimizing streaming techniques. In the case of a WebGL application, a pseudo 3D rendering of the terrain is often sufficient. But in some cases, such as visualizing small bodies with complicated 3D shapes, a true 3D rendering is necessary. The planetary DWG will analyze existing 3D transmission/streaming standards (e.g glTF9, I3S10) and will provide recommendations for the improvement of the standards, as well as the use of a particular standard depending on the use case.
For example, the planetary DWG will analyze the 3D Tiles Community Standard from OGC that brings a spatial data structure and a set of tile formats designed for 3D visualization and optimized for streaming and rendering. This Standard could be an asset for the visualization of 3D terrain as opposed to the WCS Standard which only supports a pseudo 3D visualization. However, the global mode for I3S only supports Earth-related CRS by specifying an EPSG code.
· Problem 4: Visualization of telescopic images
Ground-based telescopes (8 to 30 meters class with state-of-the-art adaptive optics) provide increasingly detailed image acquisitions of planetary bodies (planets, satellites, small bodies).
Such data are usually stored using the Flexible Image Transport System (FITS) format, which includes some support for georeferencing on planetary surfaces. A difficulty is to bridge FITS with OGC standards.
Indeed, for most ground based telescopic instruments, reduction pipelines do not provide the required spatial metadata. Astronomers must code their own image acquisition model taking into account the telescopic optical distortion, ephemerides, target shape model, projections between frameworks, physical aberrations, etc.
· Problem 5: Data discovery
There is no standard methodology for discovering the OGC services provided by the planetary community. The planetary DWG will make an inventory of existing and developing solutions. Based on this inventory, the planetary DWG will provide recommendations to the planetary community.
· Problem 6: Value-added from the planetary data system archive
The Planetary Science Archive (PSA1) and the Planetary Data System (PDS2) are active archives, internationally used, that make available well documented, peer reviewed planetary data to the research community. The data comes from orbital, landed and robotic missions, and ground-based support data associated with those missions. Currently, these archives do not provide end-user services such as web mapping services generally due to the readiness of the data (e.g., not map projected). In early 2021, National Aeronautics and Space Administration (NASA) convened a Planetary Data Ecosystem Independent Review Board which released a number of recommendations attempting to address a greater planetary data ecosystem*. Several recommendations pointed to the need for analysis-ready data (ARD) services, which many OGC standards are built to address. Fortunately, there are many groups attempting to address these limitations (e.g., data processing pipelines or on-the-fly orthorectification) across planetary research facilitates including NASA, European Space Agency (ESA), Japan Aerospace Exploration Agency (JAXA), and many others.
The Planetary DWG is being established to address the gap in the OGC baseline with regards to planetary geospatial data and to ensure knowledge is exchanged effectively between the relevant standards organizations, the OGC membership and the broader geospatial community. Although this group will not be the platform for creating new standards, the DWG will be the platform to discuss and understand existing and future issues, concerns, or barriers to interoperability to ensure that planetary data can be used effectively by the wider community.
3.3 Key Activities.
To achieve the objectives defined in this charter, the Planetary DWG will engage in the following key activities.
- Share information and experience about tools and methods for processing and publishing spatial planetary data and suggest improvements to handle georeferenced data, especially in the context of GIS technology.
- Conceive, design, coordinate, and implement demonstration, pilot, and production projects that demonstrate technical approaches to solving planetary spatial data issues using the existing mechanisms and extension capabilities in the OGC spatial data service standards.
- Collect information on planetary spatial data issues, successful technical solutions and best practices and, if considered appropriate, present them to the appropriate OGC TC or its Standards Working Groups for further actions.
- Develop and promote best practices for processing and publishing relevant planetary data.
- Manage a mailing list for discussion of domain-relevant issues within OGC.
3.4 Business Case
Commercial and open-source GIS or other spatially aware image-analysis software applications and related technologies such as remote sensing, photogrammetry, or image processing are generally written for terrestrial applications. Thus, using these software packages with planetary datasets has sometimes proven difficult or impossible. Planetary bodies such as the Moon, Mars and Venus now have numerous data layers created by different research facilities. As such interoperability of these datasets and their web applications have become extremely important.
The Planetary DWG will promote and support the establishment of requirements and best practices for web service interfaces including models and schemas related to planetary data and planetary missions, both robotic and manned for enabling:
· the discovery,
· and processing of information.
While planetary exploration is still largely a government effort, more and more commercial companies are being tasked to support exploration efforts from new orbital missions to landing rovers and humans on the Moon. Supporting the planetary domain under the OGC will obviously benefit these government endeavors but it will also benefit the many companies supporting these missions and OGC standards and services.
4.1 Planetary Domain Working Group: Business Goals
Geospatial data has been successfully standardized for Earth Observation for many years across various disciplines such as geosciences, the environment, energy, pollution, forestry, or marine sciences. This has allowed scientists to cross-reference data from various themes to broaden their research and understanding in a wider context.
The OGC interoperability standards for Earth observation data can be transposed for use in planetary data. The proliferation in planetary data, available in various wavelengths and time scales, is accompanied by an increase in data volume with the use of more and more sophisticated sensors. To cope with this increase in data volume and data sources, it is necessary to extend the Earth OGC standards for solar system celestial bodies to fully utilize the capabilities of remote interoperability protocols.
Preparation of these remote services requires processing of planetary data. Here also, the OGC standards for Earth observation must be extended to make them compatible with the specificities of planetary data.
Some special cases of planetary data (e.g., resolved measurements of small bodies; images from ground-based telescopes) will require special investigation to determine if the current OGC standards can be used or if new standards should be defined.
Moreover, with the rise of virtual reality, investigations will have to be carried out in order to study the best possibility of coupling virtual reality technologies with data access services.
And finally, all these services must be discoverable so that the tools can benefit from them. It will therefore be necessary to define queryable information and to share a common vocabulary by taking into account the initiatives that have already been carried out in the planetary science community.
The Planetary DWG has the following objectives:
1. Understand implementation barriers for the broader use of planetary geospatial data and document them in a way that can guide future work,
2. Identify interfaces and information encodings that complement the existing OGC standards,
3. Maintain a planetary CRS registry,
4. Promote the development of OGC best practices and standards in a planetary science context., and
5. Focus efforts on issues and problems in the planetary data context that result in a net gain for the community.
4.2 Planetary Domain Working Group: Mission and Role
The goal of the planetary DWG is to improve efficiency and effectiveness of spatial data users in planetary research and education in order to propagate interoperable geospatial products and other information consumables that can be shared across the community. To accomplish this, the Planetary DWG will establish a dialogue within the planetary community to develop, promote, and introduce technology relevant to that community and demonstrate the value of OGC processes and standards.
The role of the Planetary DWG is to serve as a forum within the OGC community to unite user communities interested in planetary management such as governments, vendors, industry groups, and other standards organizations (examples listed in section 5.3). The Planetary DWG will:
· Invite and receive feedback and use cases from these organizations;
· Evaluate these use cases against existing standards and architecture (including the Open Geospatial Reference Model);
· Articulate comments, identify gaps, and recognize overlaps in existing standards;
· Publish guidelines and develop requirements for the OGC Technical Committee (and other organizations) to promote interoperability and foster the development of relevant specifications and standards;
· Recommend new efforts or enhancements to existing efforts, as appropriate; and
· Propose or initiate pilot or demonstration projects and identify and attract interest from potential sponsors for these activities.
4.3 Activities planned for Planetary Domain Working Group
The Planetary DWG should be open to anyone from the planetary community whether or not they are already members of the OGC.
The following user groups will be targeted.
· Government: National, regional and local agencies, and organizations that deal with planetary spatial data.
· Private sector: Vendors, system integrators, and data providers whose activities are tied into the planetary science community.
· Academia: Research groups and advisory councils.
· The public at large, as citizens are increasingly interested in planetary data and missions.
There are currently several facilities (U.S. Geological Survey3, the Jet Propulsion Laboratory4, and Arizona State University5, etc.) that are currently supporting OGC compatible Web Mapping Servers for planetary datasets. Several commercial companies also support planetary Web Mapping Servers. We are hopeful that planetary WMS servers will soon be implemented at other NASA funded facilities, universities, and at space agencies.
The Planetary DWG will work with the International Astronomical Union working group on Cartographic Coordinates and Rotational Elements6 to update the future planetary CRS registry in the WKT representation from items published by this IAU working group.
The Planetary DWG will also work with and benefit from the Planetary Data System, which aids in the design and implementation of data-mining tools and open formats for planetary data.
The Planetary DWG will work with the International Planetary Data Alliance (IPDA7) to improve the quality of planetary science data and OGC services for end users of space-based instruments.
The Planetary DWG will work closely with other Working Groups of the OGC Technical Committee such as the Coordinate Reference System WG and the OGC API Standards Working Groups (SWGs) as well as open data formats. The Planetary DWG will maintain a rolling work program for its current and planned activities in the publicly available wiki or similar online resource. The work program will be revisited at least once a year based on the members' requests, and it will be aligned with the activities of the OGC Standards.
The Planetary DWG will work with International Heliophysics Data Environment Alliance (IHDEA8) to study the feasibility of providing both access to solar data and space weather data through OGC protocols.
The scope of work will span the following.
· Coordinate Reference Systems (CRS). The ability to define custom CRSs is the most important hurdle to overcome in order to support planetary datasets within current OGC protocols. While many of the current OGC standards may have methods to specify a custom coordinate reference system, most OGC implementations will not recognize the custom definition. For example, the most accepted method for defining a CRS is to use a European Petroleum Standards Group (EPSG) coded reference system. However, within the EPSG codes, planetary bodies are not defined. By using currently accepted body definitions as defined and regularly updated by the International Astronomical Union and International Association of Geodesy Working Group5, we can propagate these definitions into the OGC standards. Methods to facilitate this may include registering the reference systems within an OGC standards document, embedding a custom reference system with services and formats, or creating a by-reference on-line registry system. Any CRS efforts that occur within the OGC will be reported back to the International Astronomical Union and International Association of Geodesy Working Group to keep them both working toward a common goal.
· Analysis. The capability to support custom reference systems for all defined OGC Web Services is crucial for all servers and clients to calculate accurate distances, areas and angles. For example, most current generic WMS clients connecting to a planetary WMS server will default to an Earth-based CRS. Also, because many planetary mapping projects are more global in extent than Earth mapping projects, geodesic tools play an important role for accurate analysis. Supporting geodesic tools may also increase measurement accuracies for Earth-based projects.
· Formats. By expressly supporting planetary reference systems in the OGC open geospatial formats, the DWG can help facilitate usability of planetary datasets by the planetary community and the public. The recent interoperability test for GeoTIFF V1.1 already proved that the standard could handle planetary cases.
· Promotion. The working group will help promote and assist other planetary facilities to implement these standards for datasets and applications.
6. Archinal, B.A., C.H. Acton, M.F. A’Hearn, et al., 2018. Report of the IAU/IAG Working Group on Cartographic Coordinates and Rotational Elements of the Planets and Satellites: 2105, Celest Mech Dyn Astr (2018) 130:22, doi: 10.1007/s10569-017-9805-5, . http://astrogeology.usgs.gov/Projects/WGCCRE