I'm trying to find methods of finding contour and am having trouble. I've read about how surveyors do it, both with a laser and by eye/telescope, but I've seen a way to do it with a plumbob or something like that but didn't read about it. Anyone know what I'm talking about or know of other methods?
If it's any consequence, the land I am contouring is quite flat with a very gentle slope.
I've had good luck using a water level as shown in this Brad Lancaster video http://www.youtube.com/watch?v=pRjNA0DZZb4. If you pay attention to how you number the sticks as shown in the video, the larger number will be higher. I used a couple of pieces of PVC pipe I already had, and duct taped some yard sticks to them. Just be sure you reference the BOTTOM of the stick to set the yardsticks or write your numbers.
I then added a small plastic electric fence post http://www.ruralking.com/post-poly-electic-step-in-white.html?utm_medium=google&utm_source=cse&cvsfa=1908&cvsfe=2&cvsfhu=303730303430343433 by duct taping one of the pipes to it with the bottom of the pipe lining up with the bottom of the plastic part. This allows me to use this by myself. Just place the fence post portion where you want to start the countour, then place the other pipe by the first to find your "magic number". I try to put an amount of fluid in the tube so that I don't have to stoop to read it, but make sure you allow enough tube "space" above it so that it isn't forced out when you lift one or the other of the pipes too far. Once your numbers read equally for the calibration your set to go. Just move 2 to 4 feet away on your perceived contour, hold your pole plumb, then move it slightly uphill or downhill until you match your number, set a marker or flag at the base of the pole. Move further away on your contour, find your number by moving uphill or downhill, set marker, repeat. When you near the end of your tubing, just go back and get your staked pole, place it at one of your last flags, then take off again on your contour. The number should stay the same. One advantage of the water level over the A-frame is that you are not locked in to a certain distance from your last point. If you go 4 feet away from your previous point and find an obstacle (say a rock or log) you can just go back a foot or forward a foot to establish your point. The distance between your points is not critical.
One additional point is that any given point along this contour line might be an anomaly due to being on a "lump" of ground, or in a small depression. You can pay attention to any obvious oddities when you place you pole but don't obsess over it. After you have place 10 to 20 markers, sight back along your contour. You will probably see some "oddball" points, but you will also see a generalized curve developing. This "smoothed" curve is what you're after.
I also allow some of my tubing to extend above the pole. This allows me to fold the tubing over and tightly place a rubber band on it for transporting without spilling the liquid. You can also fold it over and put a rubber band on it loosely to serve as a damping effect so the liquid levels with less dancing. I am now using holding tank antifreeze as my liquid, so I can work in freezing weather, and the slight coloration makes it easier to see.
posted 7 years ago
rg, thank you so much for your timely post.
After seeing the video a few months ago, I bought some tubing and set up a bunyip using 6' metal fence posts that were at the farm. This was just a very quick set-up to show the idea to Sis and BIL when they made a trip down to help put everything up for the year. We took some time to look at contour in the camping area and talked about what modifications would have to happen before spring. On my list of things to do today is pick up an extra few 2X4's and make sure the wood-burning set is handy. After marking a couple of 2X4's I plan to split them down the middle. That way each set will match. We discussed using some sort of spike to make it easier for me to use the level when I'm alone. The step on plastic posts look like a low tech way to handle that, at least initially.
I need bunyips not so much (initially) for finding level, as to map out the hillside where I plan to build. Slope in the area is as much as 30% and the length (I bought 40') will be welcome. The RV antifreeze is also a great idea that hadn't come to me yet, but I have some in the garage. The pink should show up well against the snow, or years of leaf duff (if the snow still doesn't happen for a while).
posted 7 years ago
Chris: I wanted to suggest the possibility of using a 2 foot level instead of the plumb bob on the A-frame. When using this, I strap the level on the crossbar of the A-frame with re-usable tie wraps. The bubble level settles down much quicker than a the plumb bob. I constructed this with the uprights attached to each other with a strap hinge, and deck screws holding the crosspiece on. When stored, I take the level off for other uses, back one screw out, then fold the assembly up. There may be some pictures?
The great thing about the A-frame and water level is that they can be knocked together from any old crap and calibrated on site. The device with the carpentry level needs to be very precisely built--the legs dead even, the crossbar dead level, and so on (which is fine if you have the tools and skill). An A-frame is just 3 sticks lashed together carelessly (almost) and the a string with a weight that is calibrated on site. There are plenty of websites that tell how to do it.
I use the same type of A frame setup. I still use a plumb and a cross bar, but in addition i use a 4' water level a few feet from the bottom. The water level is much quicker and i just use the plumb part to confirm level although its probably not needed.
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