11,172 research outputs found
Integrated Navigation System: Not a Sum of Its Parts
Similar to the evolutionary process for living organisms, marine navigation systems are becoming increasingly complex and sophisticated. Both by design and function, shipboard and shore-based navigation systems are no longer individual equipment components operating independently. Instead, the trend is toward integration, data fusion and synergy. One example of this are new Performance Standards being considered by IMO to achieve a âharmonizedâ presentation of all navigation-related information on the display of an integrated navigation system (INS). Unlike a dedicated display for ECDIS or radar, the new INS displays will be a task-oriented composite presentations that enable the mariner to configure the display for an operational situation by selecting specific chart, radar, radar plotting aids (ARPA) and AIS information that is required for the task-at-hand. This paper gives a brief overview of the trend toward the development of INS. In addition to a brief summary of IMO performance standards for navigation equipment/systems, specific mention is made about a BSH (Germany) report on the âFunctional Scope and Model of INS.â A discussion is provided about the challenges of providing navigation safety information that goes beyond traditional boundaries of products and services. Currently, many agencies continue to produce individual products and services on a component basis. Hydrographic offices grapple with trying to provide multiple products and services for paper charts, raster navigational charts (RNCs) and electronic navigational charts (ENCs) while a same time, Coast Guard and Maritime Safety agencies focus on improving Aids-to-Navigation (AtoN), Vessel Traffic Services (VTS), AIS networks -- and more recently, port security. In some respects, the continued concentration on separate products and services represents an organizational reluctance to change. This in turn, results in a fragmented, sub-optimal approach to the safety-of-navigation caused by the inability to provide mariners with âseamlessâ information at reasonable cost. In particular, hydrographic offices must be willing to recognize that chart information can no longer be considered to be separate, individual products. When it comes to the provision and use of chart-related information for use in an INS, the focus needs to shift to what information is actually desired, how it will be provided, what other information it will be used with, and whether it is truly up-todate
THE ECONOMIC VALUE OF HIKING: FURTHER CONSIDERATIONS OF OPPORTUNITY COST OF TIME IN RECREATIONAL DEMAND MODELS
The paper tests two alternative specifications for the opportunity cost of time in travel cost models. The standard travel cost survey design is enriched to include a contingent valuation type question about peoples' willingness to accept compensation to forgo a precisely defined recreational experience. It is hypothesized that individually revealed value of time more appropriately reflects the opportunity costs of time associated with a particular aspect of recreation than the wage rate which measures the trade-off between work and leisure generally. The results seem to indicate a better overall fit for the models with the elicited value of individual consumer's time than for the models with the more traditional hourly earnings (wage rates). The importance of the corrected measurement of the opportunity cost time is illustrated by showing that estimated consumer surpluses based on two different value of time measurements differ significantly.Recreation demand, Travel cost model, Value of time, Resource /Energy Economics and Policy,
Protocluster Discovery in Tomographic Ly Forest Flux Maps
We present a new method of finding protoclusters using tomographic maps of
Ly Forest flux. We review our method of creating tomographic flux maps
and discuss our new high performance implementation, which makes large
reconstructions computationally feasible. Using a large N-body simulation, we
illustrate how protoclusters create large-scale flux decrements, roughly 10
Mpc across, and how we can use this signal to find them in flux maps.
We test the performance of our protocluster finding method by running it on the
ideal, noiseless map and tomographic reconstructions from mock surveys, and
comparing to the halo catalog. Using the noiseless map, we find protocluster
candidates with about 90% purity, and recover about 75% of the protoclusters
that form massive clusters (). We
construct mock surveys similar to the ongoing COSMOS Lyman-Alpha Mapping And
Tomography Observations (CLAMATO) survey. While the existing data has an
average sightline separation of 2.3 Mpc, we test separations of 2 - 6
Mpc to see what can be tolerated for our application. Using
reconstructed maps from small separation mock surveys, the protocluster
candidate purity and completeness are very close what was found in the
noiseless case. As the sightline separation increases, the purity and
completeness decrease, although they remain much higher than we initially
expected. We extended our test cases to mock surveys with an average separation
of 15 Mpc, meant to reproduce high source density areas of the BOSS
survey. We find that even with such a large sightline separation, the method
can still be used to find some of the largest protoclusters.Comment: 18 pages, 12 figure
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