The Earth Observer

Introduction

The Committee on Earth Observation Satellites (CEOS) is an international organization which aims to achieve coordination in the planning of satellite missions for Earth observation and to maximize the utilization of data from these missions worldwide. Nearly all major space organizations (NASA, European Space Agency (ESA), National Space Development Agency, Japan (NASDA), etc. are CEOS members and many major international scientific programs (IGBP, GCOS, WCRP, etc.) are CEOS affiliates.

The Global Mapping Task Team is a special task force originating out of the subgroup on auxiliary data (ADS) under the former CEOS Working Group on Data (WGD). While addressing global data sets, the ADS frequently encountered the problem that no international recommendations or standards regarding map projections exist to allow presentation of global measurements in a manner suitable for data interchange and intercomparison. Furthermore, it was recognized that the digital era of global mapping offers the potential for alternative mapping schema as the basis for processing, archiving, and distributing data. In particular, these include on-demand mapping capabilities, as well as mapping schema based on spherical tessellation of the Earth's surface rather than 2D flat map projections. The Global Mapping Task Team was established to:

• investigate the needs and directions for modern global mapping;
• facilitate the harmonization and standardization of global mapping technology; and
• chart a path for improved spatial and temporal global mapping within the next decade.

Major Objectives

• Increase awareness and provide guidance for improvement and harmonization of digital mapping for ongoing, planned, and future programs for Earth observation.
• Investigate, define, and establish a path for improved spatial and temporal global mapping of digital data within the next decade.

Tactical Plan

• Coordinate with other committees and agencies to help establish appropriate standards and promote relevant research and development activities.
• Gather advice from internal and external experts through specialized workshops and research.
• Gather and publish summaries of international information, data, and software relevant to global mapping issues.
• Provide reports on state-of-the-art for global mapping, and on needs and directions of global mapping in the next decade.
• Utilize modern electronic communication technology to maximize efficiency of gathering of information and dissemination of results.

Meetings

At the ADS-10, the subgroup explored the issue of global mapping and determined that it would be beneficial to recommend to the CEOS Plenary that a Global Mapping Task Team be established, and that the following three areas of foci be considered:

• Standard 2D map projections
• Alternative grids based on spherical tessellation
• On-demand mapping directly from native satellite sensor space

The first workshop was directed toward establishing the major objectives, tasks, and tactical plan for the CEOS Global Mapping Task Team (as listed above), and for familiarizing potential task team members with the current state and potential directions for digital mapping.

It was recognized that we are in a transition period with global mapping, driven primarily by the rapid advancement of the digital age. The 2D flat map projection paradigm in global mapping has served us well for over 2000 years when the only medium for geographical studies was a paper map or image. The digital age has altered our tools and the media for distributing and studying geographical data. Perhaps many of the challenges we currently face with regard to mapping and the interuse of gridded data sets have arisen as a result of the use of an inappropriate traditional paradigm within the new digital media.

Two alternative paradigms that will be investigated and reported on by the Task Team include: (1) alternative "ideal" mapping schema based on spherical tessellation of the globe, and (2) on-demand mapping schemes which allow data to be retained and distributed within their native spatial and temporal domains. Examples of these paradigms were presented at the meeting, as were the roles that the task team should play in the investigation and evaluation of these paradigms, as well as the future encouragement and implementation of these schemes within the global mapping communities.

Still, it was felt that there were several areas within the traditional 2D map projection schema in which the task team should provide advice and assistance. These included:

• standardization of algorithms for map projection transforms;
• increased awareness and standardization in the use of various datum standards internationally;
• advice regarding the appropriateness of different projections for different applications and regions of interest;
• advice and assistance in the measurement and specification of angular, areal, and spatial distortions within map projections; and
• recommendations concerning requirements for complete and efficient descriptions of projections and grids within data descriptors, e.g., within headers, metadata, etc.

At the recommendation of the workshop participants, a WWW home page has been established for the activities of the CEOS Global Mapping Task Team: http://vast.uah.edu/ceos/ceos.html. Within this home page will be:

• organizational notes (terms of reference, meeting agenda, and notes, etc.);
• archive and bibliography of relevant publications and reports;
• archive of relevant URL links;
• advice, data, algorithms, and software for:
  • map projections
  • datum
  • resampling schemes
  • alternative mapping schema
  • on-demand mapping schemes;
• executable demos illustrating relevant concepts; and
• Java and CORBA scripts providing relevant distributed services

Mike Botts, University of Alabama in Huntsville (UAH/GHCC)
Pete Conway, UAH/GHCC
Sam Goward, University of Maryland
David Hastings, NOAA-NGDC
Shaobo Huang, Shiba University
Susan Ingenthron, UAH/GHCC
Kent Lethco, USGS/EROS Data Center
Brian Motta, Hughes STX/MSFC DAAC
Peter Mueller, University College, London
Ron Phillips, UAH/GHCC
Achim Roth, DLR, German Remote Sensing Data Center
Gunter Schreier, DLR, German Remote Sensing Data Center.

The next meeting is scheduled for Sioux Falls, South Dakota, USA, the week of September 16-20, 1996.

For further information or if you are interested in participating in the activities of the CEOS Global Mapping Task Team, please contact Mike Botts (mike.botts@atmos.uah.edu), Chairman of the CEOS Global Mapping Task Team, or Gunter Schreier (schreier@dfd.dlr.de), Chairman of the CEOS Auxiliary Data Subgroup.

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