Compasses conventionally have been mechanical devices that utilize a pointer of magnetic material that aligns with the weak magnetic field of the Earth. The pointer for these devices is typically pivoted on a bearing and indicates the direction of the Earth's magnetic poles. Other indicia can be used to indicate the user's current heading in degrees from magnetic North.
The art and science of electronics has been applied to compasses, replacing magnetic pointers with solid-state magnetic sensors that measure the Earth's field and circuitry to process the sensor data and output information on a display. For example, existing compasses utilize microprocessor-based systems to measure the direction of the Earth's field with bi-axial fluxgate magnetometers and output this information on liquid crystal displays (LCDs). These displays typically indicate a bearing in degrees from magnetic North.
Electronic compasses have overcome many limitations of mechanical compasses, such as the slow response of the pointer pivot. There are some drawbacks of mechanical compasses, however, that have not yet been adequately solved by electronic equivalents. One is the inability to record and dynamically display a selected heading on a compass rose as a convenient reference to be used in navigational operations.
Many instances arise during which one would like to conveniently remember and recall a direction (heading). For example, a traveler may be driving a vehicle along a familiar roadway in a particular direction, and get disoriented by an unexpected detour, or by taking a side road or highway exit into an unfamiliar neighborhood. In this instance, the ability to recall the direction of the original roadway greatly facilitates reorientation.
As another example, a hiker in a wilderness often must use a compass to follow a specific bearing to reach a given destination. The hiker would be assisted by an ability to graphically record the desired course on the compass display and maintain course by simply observing deviations from this reference direction.
A third example involves the problem of returning to a particular location from a second known position. Many people often forget where they parked their car in large sports stadium or shopping mall parking lots. If such a person had a hand-held compass that could record and display a heading, the user could point the compass to the direction (heading) of the facility's entrance upon exiting the car, record the direction, then turn off the compass and proceed with their activities. When wishing to return to the car, they can display the original direction on the compass and simply follow the path in the opposite direction.
What is clearly needed is a compass with an ability to accept a user signal and record the current heading in response. The compass should also be able to dynamically display the stored heading as direction changes so the user can make course corrections and steering decisions while travelling.