Liquid compasses have a moving magnetized needle or card immersed in fluid. The use of the liquid helps to lessen excessive swing and improve readability.
Card compasses are often used on ships or boats, as they include a fixed needle and a rotating compass card, mounted in fluid. The moving card absorbs much of the boat’s motion and makes it easier to read.
Prismatic or lensatic compasses are highly accurate and often very durable. They have three main components - the base with a needle, dial, and rotating scales, a glass prism or a lens, and a lid with a hairline. Lensatic compasses allow reading the bearing while sighting on a chosen distant object. This type of compasses can either have liquid as a damping mechanism or use electromagnetic induction. Many also have tritium and a combination of phosphors which help to read the compass in the dark.
Base plate or orienteering compasses are also liquid-filled, but their main distinction is a rectangular transparent plastic base, which allows a map to be read through it. Such compasses often feature a magnifying lens for map reading, luminescent components for low-light conditions, and a ruler.
Thumb compasses are similar to baseplate compasses, but smaller in size. They can be fixed on the thumb to leave one hand free.
Top Brands of Compasses