Davis Illuminated Hand Bearing Compass
Using a Davis Instruments precision marine hand bearing compass, you can easily obtain quick magnetic bearings on shore or floating objects. Obtain a bearing simply by aligning front and rear sights on an object and reading off bearing. This compass is excellent for yachtsmen, racers, and fishermen. Uses include quick bearing or position set, determination of angular gain or loss on the competition while racing, checking distance offshore, establishing lee-bow set while cruising or racing in currents, drift vectoring, and plotting a line of position.
Features a liquid-damped compass card graduated in 5 degree segments and a large, contoured handle. This illuminated model has a solid-state LED illumination system which floods the compass capsule and sight vane with soft light. The LED will last for the lifetime of the compass. Lanyard and instructions included.
How to Use Your Davis Illuminated Hand Bearing Compass
- Hold the compass in a relaxed position at arms length, with the yellow cursor line facing you. With the compass slightly tipped so both pointers are visible, rotate your arm and upper body until both pointers are in-line with the object being sighted. Read the magnetic bearing as it appears at the yellow cursor line.
Navigating Using your Sightings
- A line of position is easy to obtain. Find an object that is easy to identify on a chart and take a sighting to determine its magnetic bearing.
- Draw a line from the object using its magnetic bearing and you know that you are somewhere along that line of position. Take a sighting of another object and plot its line of position. Your position is where the two lines cross.
Plotting Distance Offshore
- This is easiest and most accurate when your compass course is roughly parallel to the shoreline. You must also know your speed over ground.
- Note the exact time that you are abeam of (perpendicular to) or 45 degrees of a prominent object on shore like a lighthouse, smoke stack or radio tower.
- Take the exact time again when you are perpendicular to or 45 degrees off the object. Plot these sightings on the chart and, with your distance run as one leg, you have a right triangle.
- Your speed multiplied by the time equals both your distance offshore and the distance run.
Predicting Collision Course
- Take a sighting on any moving or stationary object that you suspect might be on a collision course and note its bearing. If repeated sightings yield the same bearing, you are on a collision course. Note that a collision course with a stationary object means that you are being "set" by drift or tide and you must alter course to avoid a collision.
Checking Drift While at Anchor
- Take sightings on any two or more objects on the shore and write them down. Radical changes in their magnetic bearings could indicate that your anchor is dragging.