The potential for satellite-based monitoring of groundwater storage changes using GRACE: the High Plains aquifer, Central US
Groundwater storage in the High Plains aquifer has been steadily decreasing for 50 or more years due to withdrawals for irrigation. This trend has been documented in annually published United States Geological Survey reports of water level changes in the High Plains aquifer, but assessments of groundwater storage changes in other parts of the world are incomplete. NASA's gravity recovery and climate experiment (GRACE) soon may provide an alternative means for monitoring groundwater changes, via satellite remote sensing. That terrestrial water storage changes are likely to be detectable by GRACE satellites has been demonstrated by prior studies. This investigation builds on those studies by evaluating the potential for isolating changes in the groundwater component of terrestrial water storage. In the High Plains, the magnitude of annual groundwater storage changes averaged 19.8 mm between 1987 and 1998. Uncertainty in deriving estimates of High Plains aquifer storage changes from GRACE observations will arise mainly from the removal, via land surface modeling, of the effects of soil moisture changes from the gravity signal. Total uncertainty is predicted to be about 8.7 mm.
TRECVID 2006 Overview
The TREC Video Retrieval Evaluation (TRECVID) 2006 represents the sixth running of a TREC-style video retrieval evaluation, the goal of which remains to promote progress in content-based retrieval from digital video via open, metrics-based evaluation. Over time this effort should yield a better understanding of how systems can effectively accomplish such retrieval and how one can reliably benchmark their performance. TRECVID is funded by the Disruptive Technology Office (DTO) and the National Institute of Standards and Technology (NIST) in the United States. Fifty-four teams (twelve more than last year) from various research organizations — 19 from Asia, 19 from Europe, 13 from the Americas, 2 from Australia and 1 Asia/EU team — participated in one or more of four tasks: shot boundary determination, high-level feature extraction, search (fully automatic, manually assisted, or interactive) or pre-production video management. Results for the first 3 tasks were scored by NIST using manually created truth data. Complete manual annotation of the test set was used for shot boundary determination. Feature and search submissions were evaluated based on partial manual judgments of the pooled submissions. For the fourth exploratory task participants evaluated their own systems. Test data for the search and feature tasks was about 150 hours (almost twice as large as last year) of broadcast news video in MPEG-1 format from US (NBC, CNN, MSNBC), Chinese (CCTV4, PHOENIX, NTDTV), and Arabic (LBC, HURRA) sources that had been collected in November 2004. The BBC Archive also provided 50 hours of “rushes” pre-production travel video material with natural sound, errors, etc. against which participants could experiment and try to demonstrate functionality useful in managing and mining such material.
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