The equal-altitude method (1) of determining azimuth, using the Sun as the observed body. Horizontal angles are measured from a southerly reference-point to the Sun's limbs at an identical vertical angle; if measured to the right limb before noon, it should be measured to the left limb after noon. The same limb should be observed in vertical angles. The average of the two horizontal angles, with small correction for the change in the Sun's declination during the interval from a. M. to p. M. readings, gives a resulting, horizontal angle to the meridian.