Maritime Community Research Articles

Practical Electronic Position Fixing for Small Craft

the uncertainty of the future of a suitable electronic position fixing system for small craft is reported. The importance of the small craft part of the maritime community is established. The six essential parameters of a suitable small craft electronic position fixing device are given. Five systems, Satellite, Inertial, Omega, Loran–C., and Loran–A are examined for their ability to satisfy these required parameters. Loran–A best meets the requirements, Loran–C is a close second.

OMEGA Utilization by Non-military Subscribers

A study of the OMEGA navigation system and its application to civil maritime use is summarized. Included are evaluations of various OMEGA configurations and techniques for implementing Skywave Corrections (SWC). The material presented is derived from analysis of extensive quantities of actual OMEGA phase data and from contacts within the U.S. maritime community. Four OMEGA configurations--Single Frequency, Composite, Difference Frequency and Differential--are considered in this study. Three conventional SWC implementation schemes are examined. These are the so-called Swanson, Pierce and Trapezoidal models. A simplified SWC technique based on the Swanson model is also evaluated. The above studies and maritime user contacts provide a means to suggest reasonable OMEGA configuration utilization for various environments. These include the high-seas and the coastal/confluence region. Suggestions for future studies based on these findings are presented.

National Planning for Marine Aids to Navigation-A Preliminary Report

This paper constitutes a preliminary report to the marine navigational community of the results to date of the work of the Coast Guard's Navigation Planning Staff. This staff comprises the Coast Guard participation in the joint development of the National Plan for Navigation, the concept and objectives of which were placed before the Institute at its annual meeting in June. To supplement its own study work, and in order to obtain early data upon which to base further investigation and analyses, the Coast Guard, in late May 1968 let a contract for a study of Maritime Aids to Navigation needs in the Short Distance Environment. Concurrent with this effort, the Radio Technical Commission for Marine Services agreed to convene Special Committee 60, under the Chairmanship of Commander Alfred Fiore of the United States Merchant Marine Academy, to report on the requirements for a standard system of long distance electronic aids for International Maritime use. This committee is, in effect, verifying and updating as necessary, the results previously reported on the same subject in 1957 by RTCM Special Committee 35. Preliminary results of these activities are reported herein. The textbook approach to the Navigation Aids problem dictates a three step effort. First, it is necessary to reexamine and translate into viable planning factors the navigation needs of the entire maritime community. Secondly, a definitive evaluation of current and potential technology from the smallest buoy to the most sophisticated satellite system must be accomplished. Finally, of course, the two must be combined into areas of commonality with civil aviation and defense needs identified, and a system of aids proposed which yields maximum effectiveness for the modern navigator in different fields of transportation endeavor, and at a reasonable cost. It is the purpose of this paper to bring before you initial data which will constitute relevant inputs to those analyses. To an extent, I am presenting a “Straw Man” in the hope that we may acquire comment, criticism, and additional input in any form which may serve to confirm or deny these early results and help to direct the continuing development and refinement of the factors which ultimately must act in support of the Plan decisions.

THE USE OF CHEMISTRY IN THE SYSTEMATICS OF THE LICHENS

SummaryThe extracellular metabolic end‐products that accumulate on the outer surface of the cell walls of the fungal hyphae in lichens have long been used in taxonomy. Although most morphological species of lichens are chemically uniform with regard to these substances, many others are differentiated into chemical races having distinct geographic distributions. The commonest type of chemical variation, noted in hundreds of examples, is a replacement series of the main constituent substances of the medulla. The fact that major chemical races in apparently sexually reproducing, morphologically uniform or nearly uniform lichens maintain their complete identity in places where they are sympatric suggests that such races are perhaps better regarded as distinct species. Such interpretation is further supported by the recent demonstration that where six such races are sympatric in an environmentally telescoped maritime community in Britain, the chemically different plants select different habitats, resulting in conspicuous zonation but with no alteration of plant characteristics where zones overlap. Examples of the use of lichen chemistry in genus‐level taxonomy are also given.

Tidal Current Survey of Long Island and Block Island Sounds

in direct response to navigational requirements of the yachting, fishing, and maritime community, the Coast and Geodetic Survey of the U. S. Environmental Science Services Administration is presently engaged in an intensive tidal current survey of the Long Island and Block Island Sound area. The survey is being conducted by the U. S. Coast and Geodetic Survey Ship MARMER. One hundred and sixty current stations will have been occupied by the MARMER when the three year survey is completed in 1967. From one to three meters, equally spaced in the water column, are being operated at most of the stations. New Richardson current meters are being used at 23 of the stations for 15-and 29-day series, while the older Roberts meters are being used at the remainder for 100 hours. The reference station, for prediction purposes, is The Race. The results of the survey will be used to extend the coverage and increase the effectiveness of the “Tidal Current Tables” and “Tidal Current Charts, Long Island Sound and Block Island Sound.” Of particular note is the “Supplement” to the “Tidal Current Tables”, containing the results of the 1965 field work, which was published and distributed especially for the 1966 yachting season.

The Vanishing Village: A Danish Maritime Community

The Vanishing Village: A Danish Maritime Community