Point sampling - the cruise

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Okay, it's time to cruise your timber. To use point sampling, you will need the following equipment: an angle guage or prism, compass, diameter tape, notebook, pencil, and a map. Some surveyor's ribbon is also nice to keep track of your plot center.

Each plot you are taking represents 1/10 of an acre. I generally do a 10% cruise, which means I want to take 1 plot for every acre. Since an acre is 208 feet on all sides, I generally take a plot about every 200 feet, and use a grid pattern. If you want a higher or lower percent of a survey, just adjust the distance between plot centers. For a 5% cruise, I use 300 foot centers.

I use a simple compass and pace method to get to my plot centers. You should know how many steps you need to take to get 100 feet. Simply measure 100 feet out on a flat surface. Walk from the beginning to the end and count the steps. Do it at your normal walking gait.

You will locate points on a level plane. That means, when you get into the woods, you will have to make adjustments for slope. Going up hill and your steps will be shorter. You will have to make adjustments for gait and slope. Going downhill and your steps are longer. Brushy conditions will also require you to slip a couple of steps. Point locations need not be exact. You just need to get close.

Before I start any cruise, I make a map of the area. I use the metes and bounds to make a perimeter of the area. I also need to know of a good property corner to start from. I will put the plots on the map. I usually use a North-South and an East-West type of grid. Where these lines intersect is where you want to take a point.

Plots don't have to be taken in succession on a line. You can turn up to the next line, without hurting the cruise results. This will help you get around any natural obstacles you encounter as well as helping you find the easiest route during the cruise. I will often mark my plot center with ribbon if I want to come back to it.

Starting at your known point, run your line to your first point. Anytime I encounter something different in the woods, I will mark it on my map. This could be a stream, a trail, a change in timber type, or timber sizes. The latter can be important for a cruise of a large area that has several different timber types. You can connect the dots as you reach the boundaries of the areas.

When you are at the plot center, you will want to write down as much data as you need. On the map, write your plot number. In your notebook, take note of each counted tree. I would seperate each by species, diameter, and merchantable height (number of 16'logs in a tree), as a minimum. I have also used tree grade, tree desirability (preferred, acceptable, undesirable), and tree condition in my notes, although these aren't important for volume measurements. I often note whether I would cut or leave a tree by underlining the cut trees. That gives me an idea of the amount of timber that should be removed. Keep the data for each plot seperate.

After each plot is counted, simply move on to the next plot. Each plot shouldn't take more than 5-10 minutes to locate. Best time for viewing is when the leaves are down.

After you are done with the cruise, you will be ready to crunch the numbers.

For more information, look to point sampling - the equipment, and point sampling - number crunch.

Ron Wenrich

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