Tag Archives: compass

Azimuths or Bearings?

Every year at the start of FORT 130 we start learning how to use a compass for forestry field work. Among the options is whether to get an azimuth compass or a bearings compass.

In azimuths, north is 0, east is 90, south is 180, and west is 270. This is a very commonly used system.

Bearings are a bit more complicated. The bearing is how many degrees east or west of north or south. No bearing is greater than 90. For example 45degrees azimuth is N 45 E. 225 azimuth is S 45 W. Bearings is an older system. Most land descriptions in the eastern US are in bearings. Also, bearings are ideal for field work. It is very easy to find the back sight. Keep the same number. Reverse the N/S or E/W.

True, both systems will get you where you want to go, but I will continue to emphasize bearings, partly from tradition, partly because if you learn bearings, azimuths are childs’ play.

Compass Attraction

During this week’s compass practice lab we ran into some unusual issues. A few people were using gloves with magnets one of the fingers. This magnet helps hunters free their trigger fingers. It’s a great idea, but not good when navigating with a compass.

Another student noticed that the magnetic needle on his compass was reversed; that is the white end of the needle was pointing north, instead of the red end. This is clearly a product defect and the offending compass has been returned to the manufacturer. It just shows that it is always important to check out any tools before taking them into the forest.

Compass Tips

Finding directions with a compass takes a lot of practice. But once you get it, it’s something you never forget. Here are a few tips:

1. Hold the compass level so the needle can swing freely. This is true for any model of compass.
2. When you are sighting keep both eyes open. If you squint one eye, the other will close partially too.
3. Make sure you are familiar with the bezel scale. What is the smallest unit you can read? It’s really easy to make incorrect readings.
4. Think of the line going through the compass as your line of travel. Everything lines up on this.
5. Decide when you start work if you will be using true north or magnetic north and stick with it for the whole project.
6. If you are sighting from a marker or range pole, stand back from the pole and line yourself up with the next point. Think of the direction as an extended line.

Compass practice forest mapping

Can you think of other best practices?

Using the compass


The Silva compass is a versatile tool. No forester should go into the field without a good compass. Unlike a GPS receiver it will always work. Here are a few things to keep in mind when using a compass:

— Keep it level so the needle can rotate freely.
— Avoid big belt buckles and other sources of local attraction.
— Don’t squint when sighting with the mirror.
— Relax. you will get better readings with practice and confidence.

First entry

The first class is Wednesday. I think we will start with how to use a compass. We have been using Silva Ranger compasses for a long time. They are very sturdy in the field and work well with maps. Here is a link to the Silva site and some tutorial information they have posted. It’s concise, but covers the important points.