This paper overviews firstly historical developments in marine navigation and positioning technology, secondly reviews in perspective the integration of navigation systems and concludes with an overview of the development of the electronic chart that in retrospect has passed from infancy to the state-of-the-art in less than eight years.
Today's navigators have access to positional data obtained from various radio systems such as low frequency Loran-C, Decca Navigator, and Omega, medium frequency systems typically ARGO or Hyper-Fix, ultra-high frequency systems as exampled by SERCEL Syledis and Del Norte's UHF Trisponder and microwave systems like Mini-Ranger, Trisponder and Micro-Fix. Other conventional navaids include long and short base line acoustics, the Navistar GPS and Transit Doppler satellite systems while numerous on-board sensors may include radar, RDF, depth sounder, Doppler log and gyrocompass. Consequently, the navigator is being provided with an abundance of navigational data of varying accuracy, range and resolution that he must mentally filter in terms of repeatability, reliability and relevance then subsequently transfer to a paper chart.
Despite technological advances in all these electronic aids-to-navigation, the recording and plotting of these data has evolved slowly from the conventional hand plot to today's microprocessor based systems. Today, precise filtered and integrated positional data can be overlayed on an electronic chart, stored in memory and displayed on a high speed, high resolution, colour monitor with true and relative motion capability incorporating variable survey chart scales (l). Multiple output options provide on-line data presentation on printers, plotters and RGB monitors.
Many of today's modern navigational and positioning systems used at sea relate historically to the associated developments in radio wave propagation which began with Maxwell's studies in 1865. A cursory overview of those discoveries pertinent to the development of the electronic chart are as follows(2):
1887 Hertz radio aerial invention
1893 Thompson's waveguide theory
1912 Eccles' radio-atmospheric transmission
1915 Various countries development of radio-direction finding (RDF)
1916 Royal Navy's Sonar (Asdic) and hydrophones
1918 Watson's radio ground wave propagation
1926 Yagi's directional radio aerial
1930 Lilienfield MOS/FET Transistor
1944 Decca's Main Chain
1952 Loran radio navigational system
1960's U.S. Federal Government began collecting digital cartographic data
1964 U.S. Navy's Transit navigational satellites (NNSS)
1968 U.S. Navy and Sperry developed "HICANS"
1976 U.S. Navy, U.S. Coast Guard and Sperry developed Command Display and Control System "COMDAC"
1979 OSPS' PNS electronic chart systems development
1980's Defense Mapping Agency Automated Notice to Mariners System "ANMS
1980 U.S. Navy's and Hughes developed their Submarine Advanced Combat System "SUBACS" and Plotter and Combat Systems Display "PACS"
1981 Automatic radar plotting aids "ARPA"
The first electronic chart workshop was held in Fredericton, N.B. in 1982i the second in Baltimore, MD in 1983 and in September 1984 electronic charts were discussed in the international community at Plymouth, England at the International Hydrographic Technical Conference. Three IHO groups are now involved with studies related to electronic charts: The Committee in the Exchange of Digital Data, the subcommittee on Future Chart Design and the Elec