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CONTENTS10th Anniversary Celebration in Berlin
Report from CEOS 8th Plenary in Berlin
10th Anniversary Celebration in Berlin
Integrated User Data Requirements for Global Change Research
CEOS Special Report on Successful Applications of Earth Observation Satellite Data (Pilot Version)
Advancing Global Topographic Kowledge: Significant Progress,---This page but CEOS Members Can Help Greatly
Advancing Global Topographic Kowledge: Significant Progress, but CEOS Members Can Help Greatly(continued page)
CEOS Activity Plan for 1995/News Highlights/CEOS Meeting Calendar
Advancing Global Topographic Knowledge:Significant Progress, but CEOS Members Can Help Greatly!
David A. Hastings
National Oceanic and Atmospheric Administration
National Environmental Satellite, Data,
and Information Serveice National Geophysical Data Center
Gunter Schreier
German Aerospace Research Establishment
German Remote Sensing Data Center
Global topographic data are among the most important data sets for many scientific, technical, and other applications.
- Digital elevation models (DEMs) have almost unlimited applications.
They can be used to help rectify satellite-derived data, such as the Normalized
Difference Vegetation Index or high resolution synthetic aperture radar
data, for making ortho-images for improved accuracy in comparisons over
time. They can be used to optimize the development of new cellular communications
infrastructures. Even when not used directly in a study, topographic data
are often used in preparing visualization tools such as perspective or
stereoscopic views of terrain.
However, high-quality, accessible, global coverage of digital elevation data is sorely lacking. There are sources of DEMs in space (notably stereoscopic satellite imagery), but there are no operational programs that offer inexpensive unrestricted high-quality global DEM coverage from any source. Although some dedicated space missions to map global topography are being considered, none is a certainty. The current reference model is ETOPO5, distributed by the National Geophysical Data Center. It includes some 10-arc-minute grids and some 5-minute grids, all presented at a 5-minute gridding.
The CEOS Working Group on Data Auxiliary Data Subgroup, and several organizations around the world, are helping to coordinate an attempt to address this problem of quality global DEM coverage. The effort is called the Global Land One-kilometer Base Elevation (GLOBE) project, not to be confused with several other projects that use the same acronym. The GLOBE project is developing a 1-km gridded, quality-controlled global DEM. The final product is scheduled for release in 1996. The general aims of GLOBE are:
1. Develop a 1-km global DEM, by including the best available data sets and by encouraging specialists to participate in production and review of the data. The GLOBE DEM will be made available to the worldwide research community, perhaps on 8-mm tape or CD-ROM. There may be two versions of GLOBE:
"BAD GLOBE" based on the Best Available Data (BAD), even if some data are restricted from general distribution. This version would be distributed in accordance with whatever agreement is negotiated witth contributors of various copyright data sets. High-quality restricted data may improve the usability of those data for people having permission to use such data. Nevertheless, data not available to everyone are of limited value in promoting scientific advances (and the social benefits therefrom).
"GOOD GLOBE" based on Globally Only Open-access Data (GOOD). This is the primary aim of GLOBE: to produce an unrestricted DEM that is the most useful database to everyone.
2. Strengthen international collaboration in the development of research-quality digital global data sets. Advance technical and cultural capabilities for international collaboration in the development of such data.
3. Strengthen social awareness of the need for optimal quality high-resolution global topographic information, including the provision of a focus for the timely release of currently restricted terrain data sets.
4. Supply a "pathfinder" data set to the Earth observation community.
5. Develop a data structure (nested multi-resolution grid system) useful for future enhancements such as might come from future topographic satellite mission.
6. Give the Committee on Earth Observation Satellites Working Group on Data (CEOS-WGD) a prototype in cooperatively improving vital data. Input data and methods used for GLOBE are:
* Elevation contours from the 1:1,000,000 Operational Navigation Charts digitized into the Digital Chart of the World (DCW) will be gridded at 1-km nominal latitude-longitude spacing.
* Currently available high-resolution DEMs at higher resolution than GLOBE's will be sampled and inserted into GLOBE.
* DEMs derived from satellite imagery (stereo-optical and radar) and altimetry will be added to GLOBE where applicable.
* Available data from the 3 sources above do not currently provide global coverage, so GLOBE coverage will be filled out by resampling lower-resolution DEMs (for which there is global coverage) into GLOBE.
Documentation on sources, methods of derivation, quality control procedures,
and data characteristics will be provided as text and figures/maps. Additional
data, such as global hydrological networks, land-sea masks, and terrain
slope information, are expected to be developed as byproduct digital data
sets.
Several specialists/institutions have jointly developed the GLOBE project,
which has been approved by tthe Auxiliary Data Subgroup of CEOS-WGD. The
International Geosphere-Biosphere Programme's Office of Data and Information
Systems is also participating in GLOBE design & evaluation efforts.
Since its formation early in 1992, the GLOBE project has conducted meetings
about every 6 months. It has developed prototype methods of adapting high
resolution DEMs and Digital Chart of the World contours to GLOBE-resolution
DEMs, and for adapting contributed lower-resolution DEMs to GLOBE scale.
GLOBE was recently given a significant boost by a major contribution
of data by the U.S. Defense Mapping Agency. DMA, in conjunction with GLOBE
participants, derived a 30-arc-second model from selected DMA coverage,
as a contribution to GLOBE.
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