Marcq St. Hilaire Method. Procedure for finding ship's position line from an observation of a heavenly body and the calculation of the altitude and azimuth it would have if ship were at estimated position. The difference between the calculated altitude (or zenith distance) and observed altitude (or zenith distance) is the error in locus of assumed position line. The position line is moved towards or away from the geographical position of the observed body according to the amount the two altitudes (or zenith distances) differ.
Mareel. Shetland name for phosphorescence of the sea.
