October 2007 Archives

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.

Can you think of other best practices?

I will be speaking to the Intro to Forestry class on reforestation in Africa. I decided to put together a Google map of the places I have visited or worked in. There are a lot of pins in the map. I will add pictures and more cities I've visited later.

View Larger Map

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.

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.

Tomorrow I'm giving a talk at the library on my trip to Guinea last December. It's part of a library sponsored series on trips faculty have made. George Siehl will talk about his trip to Kenya and Beth Brantley will highlight Burundi. Here is a Google map with each of our visits marked:

View Larger Map

I put my pictures in a PowerPoint presentation. I thought about putting the presentation online, but it was 18 megabytes, which would take forever to load. So, here is a link to some of the pictures I loaded on Flickr.

As GPS receivers become more widely used by foresters it's important to get a good idea on how accurate they are under tree cover. A fully closed canopy may completely block the signal, or it may be only available in patches.

There have been some research projects on GPS accuracy in the forest. Follow this link to a summary of a research article by Paul Bolstad in the Northern Journal of Applied Forestry. The research team tried several models of GPS receivers under conditions ranging from open field to closed canopy. Their results are very interesting.

Note that the presentation works best in MS Internet Explorer. If you prefer, here is a link to the original PowerPoint file.