LOP Navigation

Here is the history of the development of the Line of Position (LOP) method for finding one's position on a chart from observations of the sun, the moon, the planets or the stars using a sextant.

The first chapter sets the stage by describing the common navigation techniques mariners used in the early eighteenth century. The second chapter tells the story of Captain Thomas H. Sumner's conception of his "parallels of equal altitude" off the coast of Ireland in 1837. Marcq Saint-Hilaire's simplification of Sumner's method using assumed positions is described in the third chapter. The final chapter brings the method up to the present time by illustrating the simplified methods that were developed in the twentieth century, largely in response to the needs of the aviators.

The principle historic value of Line of Position Navigation is the accurate reprint of the first edition of Sumner's 1843 book in its entirety in Appendix A. Here Sumner describes his method in detail and gives examples of how it can be used. In a similar historic vein, Appendix B provides translations of two original French 1870's publications of Saint-Hilaire's "assumed position" methods. Appendix C contains detailed explanations and derivations of a number of Saint-Hilaire's equations.

Michel Vanvaerenbergh is a qualified commercial airline pilot and instructor. He taught aircraft navigation at the National Belgian Ecole d'Navigation and wrote the course that is still in use there.
Peter Ifland is a retired Commander in the U. S. Naval Reserve and served as a deck officer on destroyer types. He holds a PhD in chemistry and spent his professional career as a Manager of R&D for a multinational consumer products company. Click Here to learn about his book on the history of the sextant: Taking the Stars, Celestial Navigation from Argonauts to Astronauts.

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For an autographed copy of Line of Position Navigation

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