Some Compasses

Recta Baseplate Compass

Recta Baseplate Compass The baseplate compass comprises a transparent base plate holding the rotatable, transparent compass housing. 0 to 360 degrees are marked around the black bezel fixed on the circumference of the housing. 0 degrees is marked N, 90 degrees is marked E, 180 degrees is marked S and 270 degrees is marked W. Parallel red N-S lines are marked on the base of compass housing. The compass needle rotates freely on a pivot and floats in liquid so it can move freely when horizontal, the red end pointing to magnetic north. A red direction arrow is marked along the long centre line of the baseplate away from the compass needle's pivot.

the baseplate compass is used to show the walking direction as follows. Mark the point on a map where you are now. Mark the point on the map to where you want to walk to in a straight line. Draw a straight line on the map between the two points. Place the red direction arrow or the long edge of the baseplate over the line drawn on the map, ensuring the red arrow points in the direction you wish to go. Holding the baseplate compass firmly on to the map, rotate the compass housing until the the parallel red N-S lines on the base of the compass housing are parallel to and in the same direction as N-S lines on the map. Picking up the compass by the baseplate, leaving the compass housing in position, the bearing, the angle between grid north and the direction of travel can be read directly from the bezel. The difference between grid north and magnetic north can be corrected for by turning the bezel.

The compass may be worn when walking with the lanyard around the neck, hopefully avoiding disturbing the setting of the compass housing. To check direction of travel, holding the baseplate horizontally it can be turned until the compass needle is parallel to and in the same direction as the N-S lines on the base of the compass housing, the red needel boxed in by the two thick red N-S lines . The red direction arrow marked along the centre line of the baseplate now points the way to go.

Wilkie Mirror Compass

Wilkie Mirror Compass Uncle jack gave to me this walking compass over 50 years ago. It was made by a company called Wilkie of Germany. The Compass Museum describes Wilkie as one of the most important german compass manufacturers and show several of their products.

The Wilkie walking compass comprises a black plastic compass housing containing the magnetic needle with a rotatable double scaled dial and a mirrored hinged cover. The two scales are marked as 0 to 360 degrees and from 0 to 64(00) mils around the circumference of the dial. 0 degrees is marked N, 90 degrees is marked E, 180 degrees is marked S and 270 degrees is marked W. The compass needle rotates freely on a pivot. It is not liquid filled. When the cover is closed a lever locks the compass needle at a fixed position.

The mirror compass is used to find the bearing of a distant point. To use, open the cover of the compass and align it so the reflection of the compass dial is clearly visible in the mirror when the sighting line is aimed at the distant point. Adjust the compass so the sighting line in the mirror is passing directly through the center of the compass wheel. Ensuring the compass needle can move freely, rotate the compass dial until the north tip of the needle is pointing at the N on the dial. You can then read the bearing of the target by reading compass dial at the index point.

Silva Expedition 54

Silva Expedition 54 The Silva Expedition 54 can act as a combined baseplate compass and mirror compass. Its manual can be found here. The operation as a baseplate compass is given as follows.

" The Silva System 1,2,3.
  1. Place the compass on map with edge along the line of travel.
  2. Rotate the capsule until the "N" on the compass dial points to the magnetic north on the map. Make sure that the North-South lines are parallel with the maps meridians.
  3. Hold the compass level in front of you and turn your body until the cards "N" is directly over the North arrow in the compass housing. The direction of travlel arrow now points precisely to your destination. Look up, sight on a landmark and walk to it. Repeat this procedure until you reach your destination.
Course Setting from map or Sea Chart
  1. Use the Silva System stages 1 and 2.
  2. Note the bearing indicated on the outer dial graduation at the index mark.
  3. Turn the compass housing so that the line of sight through the magnifying lens to the mirror is at right angles to the long sides of the baseplate. By viewing through the optical system, with the compass kept horizontal turn the complete compass until the hairline is in line with the bearing required on the card scale. The line of sight is now giving the bearing.
Plotting Location or Taking Cross bearing to the map or Chart.
  1. Read through the optical system the compass bearing of any object you are able to identify on your map or chart.
  2. Set the compass housings outer dial graduation to the same bearing as obtained through the optical sight.
  3. Place the compas on the map or chart with one side or direction of travel over the object. Keeping the object under the same line turn the whole compass until the North-South lines are parallel with the closest meridian. Check the "N" on the outer dial graduation ring is towards the North on the map.
  4. Your position is somewhere along the line that passes through ther object.By taking another cross bearing, that is by repeating the above 3 stages using another object, your position will be where the lines through the objects intersect. Greater accuracy will be achieved with an angle of 90 degress between the sighting lines. "

Some Norths

A. True North (and South) are at the geographic poles which are the points where the earth's axis meet the surface. In the northern hemisphere, the position of the North Pole is indicated by the Pole Star which itself can be located by following the pointers from the Plough.

B. Grid North is used to orient Ordnance Survey maps. It differs slightly from true north.

C. Magnetic North/South is the axis along which a compass needle will align itself in the Earth's magnetic field. Magnetic North is not the same as Grid North.

In the bottom right corner of OS Landranger Map 161, the section on Techical Information gives the differences between true north and grid north at the sheet corners. Magnetic North is given as 2 degrees 11 minutes ( 39 mils) west of grid north at the centre of the sheet on July 2009. Magnetic north varies with place and time.

Some Websites

There are many websites interested in compasses.

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8 * 24 Binoculars

The first number (8x) is the magnification, meaning the image of the subject you see through the binocular is 8 times larger than visible with the naked eye. Objects at 100 yards appear only 12.5 yards away (100 yards divided by 8). The second number (24) is the diameter of the objective lenses in millimeters. This is a major factor in determining how much light enters the binocular.