Other features found on modern orienteering compasses are map and romer scales for measuring distances and plotting positions on maps, luminous markings on the face or bezels, various sighting mechanisms (mirror, prism, etc.) for taking bearings of distant objects with greater precision, gimbal-mounted, "global" needles for use in differing hemispheres, special rare-earth magnets to stabilize compass needles, adjustable declination for obtaining instant true bearings without resorting to arithmetic, and devices such as inclinometers for measuring gradients. The sport of orienteering has also resulted in the development of models with extremely fast-settling and stable needles utilizing rare-earth magnets for optimal use with a topographic map, a land navigation technique known as "terrain association". Many marine compasses designed for use on boats with constantly shifting angles use dampening fluids such as isopar M or isopar L to limit the rapid fluctuation and direction of the needle.