In the study of the Earth's magnetic field , the term isogon or
isogonic line refers to a line of constant magnetic declination , the
Kaynak: Contour lineThe Fermat point has a near-identical twin called the first
isogonic center or X(13) and it is important not to confuse the two.
Kaynak: Fermat point1st
isogonic center: Let A'BC be the equilateral triangle having base BC and vertex A' on the negative side of BC and let AB'C and ABC' be
Kaynak: Triangle centerhas been adjusted to indicate true north instead of magnetic north (as long as the compass remains within an area on the same
isogonic line).
Kaynak: Magnetic declinationInformation on declination for a region can be represented by a chart with
isogonic lines (contour lines with each line representing a
Kaynak: Earth's magnetic fieldused his voyages on the pink Paramour to study the magnetic variance and was able to provide maps showing the halleyan or
isogonic lines.
Kaynak: History of longitudeThis was the first such chart to be published and the first on which
isogonic , or Halleyan, lines appeared. File:Edmond Halley plaque in
Kaynak: Edmond Halleyand an
isogonic tetrahedron has concurrent cevians that join the vertices to the points of contact of the opposite faces with the
Kaynak: Tetrahedron