A fix is called a "running fix" when one or more of the LOPs used to obtain it is an LOP advanced or retrieved over time. In order to get a fix the LOP must cross at an angle, the closer to 90° the better. This means the observations must have different azimuths. During the day, if only the Sun is visible, it is possible to get an LOP from the observation but not a fix as another LOP is needed. What may be done is take a first sight which yields one LOP and, some hours later, when the Sun's azimuth has changed substantially, take a second sight which yields a second LOP. Knowing the distance and course sailed in the interval, the first LOP can be advanced to its new position and the intersection with the second LOP yields a "running fix".