Reports
LORAN-C calibration in Chesapeake Bay
1987, Halka, J.P.
Report of Investigations 47
Abstract
LORAN-C has become, in recent years, the primary radionavigation system utilized in nearshore waters due to its wide geographic coverage, operational reliability and the continued reduction in cost of receivers for shipboard use. Vessels operated by the State of Maryland have come to rely more heavily on this system since operation of the State-owned Raydist radionavigation system was discontinued in 1984.
As with all navigation systems the intended purpose of LORAN-C is to enable a vessel at sea to determine its location. There are two important aspects of this determination: accuracy and repeatability. Accuracy is the ability to arrive at a predetermined location at sea or, conversely, to plot a location on a chart once a navigation fix has been obtained. Repeatability refers to the ability to return to a location at which a navigation fix has previously been obtained. The locational capability of LORAN-C signals or other radionavigation transmissions with respect to these two components is quite different. The work reported in this paper primarily concerns an improvement in the accuracy of position determination in the Chesapeake Bay through the development of regional correction factors; however, repeatability is generally discussed because of its dependence on LORAN-C signal propagation and its effect on user expectations for precise navigation. The results of this effort have been incorporated into a computer program, included in the appendix, which permits conversion between LORAN-C time differences for the X and Y lines of position and latitude and longitude coordinates referenced to the North American Datum of 1927 (NAD-27).
