Focal Length The distance from the center of a lens (or, the secondary principal point, if it has) to the focal point (sensor) The longer the focal length, the narrower is the angle of view More details
Abbreviation for altitudes over 18,000 feet For example: 31,000 feet = FL 310 Flight levels are always measured in feet and in pressure altitude (see also Pressure Altitude)
The forestay length measured from where the forestay meets the deck, or from the jib outhaul in the case of a bowsprit, to the forestay attachment point on the front of the mast or to where the forestay intersects the front of the mast, projected if necessary