2,373 research outputs found
Evaluation of radiometric and geometric characteristics of LANDSAT-D imaging system
With vegetation masked and noise sources eliminated or minimized, different carbonate facies could be discriminated in a south Florida scene. Laboratory spectra of grab samples indicate that a 20% change in depth of the carbonate absorption band was detected despite the effects of atmospheric absorption. Both bright and dark hydrothermally altered volcanic rocks can be discriminated from their unaltered equivalents. A previously unrecognized altered area was identified on the basis of the TM images. The ability to map desert varnish in semi-arid terrains has economic significance as it defines areas that are less susceptible desert erosional process and suitable for construction development
Gauge transformations in the Lagrangian and Hamiltonian formalisms of generally covariant theories
We study spacetime diffeomorphisms in Hamiltonian and Lagrangian formalisms
of generally covariant systems. We show that the gauge group for such a system
is characterized by having generators which are projectable under the Legendre
map. The gauge group is found to be much larger than the original group of
spacetime diffeomorphisms, since its generators must depend on the lapse
function and shift vector of the spacetime metric in a given coordinate patch.
Our results are generalizations of earlier results by Salisbury and
Sundermeyer. They arise in a natural way from using the requirement of
equivalence between Lagrangian and Hamiltonian formulations of the system, and
they are new in that the symmetries are realized on the full set of phase space
variables. The generators are displayed explicitly and are applied to the
relativistic string and to general relativity.Comment: 12 pages, no figures; REVTeX; uses multicol,fancyheadings,eqsecnum;
to appear in Phys. Rev.
Evaluation of radiometric and geometric characteristics of LANDSAT-D imaging system
Problems, accomplishments, and significant results associated with the evaluation of the LANDSAT-D thematic mapper system are outlined. The higher resolution (over MSS) causes the TM data to approach more closely the quality of high altitude photographs. Thus far, it appears that the data can be used for map inspection and in certain instances for limited map revision. Image maps can be made at a scale of 1:100,000 and perhaps up to 1:62,500. It was also shown that TM data can help locate rocks containing minerals with high hydroxol content, such as clays, gypsum, alunite, and sericite
Temporal and spatial dynamics of CO2 air-sea flux in the Gulf of Maine
Ocean surface layer carbon dioxide (CO2) data collected in the Gulf of Maine from 2004 to 2008 are presented. Monthly shipboard observations are combined with additional higher‐resolution CO2 observations to characterize CO2 fugacity ( fCO2) and CO2 flux over hourly to interannual time scales. Observed fCO2 andCO2 flux dynamics are dominated by a seasonal cycle, with a large spring influx of CO2 and a fall‐to‐winter efflux back to the atmosphere. The temporal results at inner, middle, and outer shelf locations are highly correlated, and observed spatial variability is generally small relative to the monthly to seasonal temporal changes. The averaged annual flux is in near balance and is a net source of carbon to the atmosphere over 5 years, with a value of +0.38 mol m−2 yr−1. However, moderate interannual variation is also observed, where years 2005 and 2007 represent cases of regional source (+0.71) and sink (−0.11) anomalies. We use moored daily CO2 measurements to quantify aliasing due to temporal undersampling, an important error budget term that is typically unresolved. The uncertainty of our derived annual flux measurement is ±0.26 mol m−2 yr−1 and is dominated by this aliasing term. Comparison of results to the neighboring Middle and South Atlantic Bight coastal shelf systems indicates that the Gulf of Maine exhibits a similar annual cycle and range of oceanic fCO2 magnitude but differs in the seasonal phase. It also differs by enhanced fCO2 controls by factors other than temperature‐driven solubility, including biological drawdown, fall‐to‐winter vertical mixing, and river runoff
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