One of the specialty types of magnetic compasses, the prismatic compass makes use of a small capsule that is filled with oil and a magnetized dial. This combination is augmented with an illumination component that helps to provide one of the most accurate compass readings of any type. Sometimes referred to as an optical compass, the pinpoint accuracy of the device helps to make it ideal for a number of applications where lighting is in limited supply.
All types of compasses allow the user to isolate a direction from any point on the planet. The pointer within the device will align with the pull of the natural magnetic field of the Earth, ensuring that it will make it easy to accurately determine the basic directions of north, south, east, and west. It is not unusual for a magnetic compass to be used as part of an overall navigation process, with such devices as chronometers and sextants used to further refine the process of plotting a course.
Due to the luminescent qualities that some prismatic compasses have, they are ideal for use in any environment where visibility is somewhat limited. When navigating through an underground system such as a cave, it will provide a reliable means of reading direction, helping to prevent the explorer from becoming lost. Applications within the professions that depend on surveying land and other property also often make use of this compass.
Perhaps one of its most common uses is with any task or profession that involves waterways or the ocean. Marine biologists can make use of the compass when conducting underwater explorations, making it easy to record directions to and from a starting point. The device can be especially helpful in deeper waters, where there is very little light.
Generally, the prismatic compass is designed to handle heavy-duty use, and it is both air and watertight. Many models can be mounted on a tripod when appropriate, as well as held and operated in one hand. Some are illuminated with the assistance of a small battery, while others use photoluminescent materials to make the dial visible in low light environments.