How to Use a Silva Thumb Compass

The sport of orienteering involves point-to-point navigation in wilderness areas using topographic maps and a compass. Travel is on foot and the pace is fast, demanding a high level of physical fitness, in addition to navigational skills. Orienteers use traditional protractor compasses with degree markings for precise bearings to and from landmarks. Thumb compasses like the Silva Jet Spectra, attached to the thumb of the hand holding the map, are also utilised to provide rougher, at-a-glance guidance and continuous alignment of the compass with the map while on the run. The needle always represents the direction of travel on the map indicated by the thumb. The outer ring of the Silva Jet Spectra is colour-coded for quick visual reference of needle position. Minimal markings on the transparent baseplate allow full visibility of the map.

Fold the topographic map to an appropriate carrying size with the north-south magnetic meridian lines on the map parallel to the folded edges.

Orient the map so the meridians are pointing north and south.

Locate your present location and the desired destination on the map.

Strap the Silva Jet Spectra on the thumb of the hand holding the map.

Place your thumb with the Silva Jet Spectra on the map, pointing in the direction of your destination.

Turn your body and face the correct direction of travel.

Note which coloured segment on the compass ring the compass needle is pointing to. Stay on course by keeping the compass needle aligned with that colour.

Move your thumb forward on the map as you run, keeping the terrain on the ground around you aligned with the terrain features on the map.

Verify your direction with the compass needle every time you check the map. Reconcile your position on the ground with your position on the map constantly as you move toward your destination.

Cite this Article A tool to create a citation to reference this article Cite this Article

About the Author

Gus Stephens has written about aviation, automotive and home technology for 15 years. His articles have appeared in major print outlets such as "Popular Mechanics" and "Invention & Technology." Along the way, Gus earned a Bachelor of Arts in communications. If it flies, drives or just sits on your desk and blinks, he's probably fixed it.