The advantages of using unmanned underwater vehicles in coastal ocean studies are emphasized. Two types of representative vehicles, remotely operated vehicle (ROV) and autonomous underwater vehicle (AUV) from University of South Florida, are discussed. Two individual modular sensor packages designed and tested for these platforms and field measurement results are also presented. The bottom classification and albedo package, BCAP, provides fast and accurate estimates of bottom albedos, along with other parameters such as in-water remote sensing reflectance. The real-time ocean bottom optical topographer, ROBOT, reveals high-resolution 3-dimentional bottom topography for target identification. Field data and results from recent Coastal Benthic Optical Properties field campaign, 1999 and 2000, are presented. Advantages and limitations of these vehicles and applications of modular sensor packages are compared and discussed. 相似文献
In 1994, 1995, and 1996, seagrasses in 46 of the 89 coastal embayments and portions of seven open-water near-shore areas in
Massachusetts were mapped with a combination of aerial photography, digital imagery, and ground truth verification. In the
open-water areas, 9,477.31 ha of seagrass were identified, slightly more than twice the 4,846.2 ha detected in the 46 coastal
embayments. A subset of the 46 embayments, including all regions of the state were remapped in 2000, 2001, and 2002 and again
in 2006 and 2007. We detected a wide range of changes from increases as high as 29% y−1 in Boston Harbor to declines as large as −33% y−1 in Salem Harbor. One embayment, Waquoit Bay, lost all of its seagrass during the mapping period. For the 12-year change analysis
representing all geographic regions of the state, only three embayments exhibited increases in seagrass coverage while 30
of the original 46 embayments showed some indication of decline. For the decadal period, rates of decline in the individual
embayments ranged from −0.06% y−1 to as high as −14.81% y−1. The median rate of decline by region ranged from −2.21% y−1 to −3.51% y−1 and was slightly less than the recently reported global rate of decline for seagrasses (−3.7% y−1). Accounting for the gains in three of the embayments, 755.16 ha (20.6%) of seagrass area originally detected was lost during
the mapping interval. The results affirm that previously reported losses in a few embayments were symptomatic of more widespread
seagrass declines in Massachusetts. State and Federal programs designed to improve environmental quality for conservation
and restoration of seagrasses in Massachusetts should continue to be a priority for coastal managers. 相似文献
BURNING BUSH: a fire history of Australia by S.J. Pyne. 15 × 23 cm, xix + 520 pp. Allen & Unwin, Sydney 1992. (ISBN 1–86373–194–6) $19–95 (soft).
ADVANCES IN RESOURCE MANAGEMENT: tributes to W.R. Derrick Sewell edited by H.D. Foster. 15 × 23 cm, viii + 366 pp. Belhaven Press, London 1992 (ISBN 1–85293–292‐ 9) £39.50 (hard).
FEMINISM AND GEOGRAPHY: the limits to geographical knowledge by G. Rose. 15 × 23 cm, 205 pp. Polity Press, Cambridge 1993. (ISBN 0–7456–1156–7) $34.95 (soft).
EVERYDAY LIFE: women's adaptive strategies in time and space (Lund Studies in Geography, Ser.B Human Geography 55) by T. Friberg (translated by M. Gray). 16 × 24 cm, 217 pp. Lund University Press, Lund, and Chartwell‐Bratt, Bromley 1993. (ISBN 0‐ 86238–345–5)
NATURAL DISASTERS by D. Alexander. 16 × 23 cm, xix + 632 pp. University College London Press, London 1993 (ISBN 1–85728–094–6) $55.00 (soft). 相似文献
This paper presents an analysis of a neglected area of study by geographers; that of resident action groups. During the 1980s there has been a significant increase in the number of resident action groups throughout Sydney. Resident activism has influenced local planning processes, the location of noxious facilities and subsequent urban form. This has initiated important reactions by government at both the local and State levels. Urban collective activisms have been hypothesised as single‐issue, self‐serving nimby groups. However, RAGs are also empowering forces, in which women and men are introduced to the political structures and become engaged in protest and resistance that can challenge the social and spatial order. RAGs can, either singularly or cumulatively, force a re‐aligning of existing power relations, and they can necessitate changed modes of governance (or govern‐mentality). 相似文献
Using a calibrated bio-optical model we determined that the optical water quality conditions in several nitrogen-impaired embayments and in one unimpaired system were within the range of values known to support eelgrass growth. We also used the model to identify a range of light requirements for eelgrass (Zostera marina). Higher eelgrass light requirements, expressed as a percentage of surface-incident irradiance, corresponded with higher sediment organic matter content. These results corroborated findings by previous studies which indicate a generalized relationship: seagrasses growing in turbid conditions with poorer water and sediment quality have higher light requirements than those growing in less degraded conditions. The mechanistic reason for the variation in light requirements is still not completely explained and cannot be attributed to a single independent variable. Varying light requirement have important implications for eelgrass protection and should be considered when setting restoration targets for eelgrass in water quality and nitrogen remediation programs. 相似文献