Poor Man's Surveyor Transit
Intro: Poor Man's Surveyor Transit
The challenge: determine the grade of our back yard for a pond.
The problem: I’m broke
The solution: a home-made transit that I can use to shoot a grade.
A transit does a simple thing. It looks strait across a space to a ruled pole. Commercial transits use a scope with magnification in order to read the ruled pole held by an assistant. The scope has to be level . It must provide a way to show direction/bearing. If I could figure all that out I had a tool I could use.
The problem: I’m broke
The solution: a home-made transit that I can use to shoot a grade.
A transit does a simple thing. It looks strait across a space to a ruled pole. Commercial transits use a scope with magnification in order to read the ruled pole held by an assistant. The scope has to be level . It must provide a way to show direction/bearing. If I could figure all that out I had a tool I could use.
STEP 1: Basic Construction
In making a transit the complicated part comes in making sure the view is straight across, level, and in measured directions. I had to build something that would fit on a tripod, sit level, provide a strait-line view preferably with magnification. Finally, it had to determine direction or bearing.
To begin I would need a base that mounts on the tripod and then a platform to hold the scope. Then there would be a secondary platform that is adjustable so that it is level. That means the upper platform had to somehow sit above the lower one on a pivot point and have some way to indicate direction. The latter I left to last. The rest I figured out as I went along.
I cut a base out of a piece of particleboard shelving for the base. It was circular, about eight inches. I cut another piece for the second platform about an inch smaller. To mount the base on the tripod I drilled a hole in the center of the base and put in a ¼” bolt anchor in it for the tripod bolt. I used part of an outdoor light fixture with an oval shape to provide a means of pivoting the second platform. The top platform fastens to the bottom by passing a bolt through a hole in the center of the top platform and into the top of the anchor. I used an eye bolt so it would be easier to tighten.
I drilled three holes in the upper platform and inserted anchors through which I screwed ¼” eyebolts. This allowed the top platform to be adjusted in three directions. For the scope mount I cut a couple of uprights out of pine with notches to hold the scope. I mounted the uprights on the top platform and put screws through the sides to hold the scope.
To begin I would need a base that mounts on the tripod and then a platform to hold the scope. Then there would be a secondary platform that is adjustable so that it is level. That means the upper platform had to somehow sit above the lower one on a pivot point and have some way to indicate direction. The latter I left to last. The rest I figured out as I went along.
I cut a base out of a piece of particleboard shelving for the base. It was circular, about eight inches. I cut another piece for the second platform about an inch smaller. To mount the base on the tripod I drilled a hole in the center of the base and put in a ¼” bolt anchor in it for the tripod bolt. I used part of an outdoor light fixture with an oval shape to provide a means of pivoting the second platform. The top platform fastens to the bottom by passing a bolt through a hole in the center of the top platform and into the top of the anchor. I used an eye bolt so it would be easier to tighten.
I drilled three holes in the upper platform and inserted anchors through which I screwed ¼” eyebolts. This allowed the top platform to be adjusted in three directions. For the scope mount I cut a couple of uprights out of pine with notches to hold the scope. I mounted the uprights on the top platform and put screws through the sides to hold the scope.
STEP 2: Making It Functional
I mounted a level on the top platform.
The only thing I had that would work for a scope was a spotting scope for a telescope. I mounted it in the uprights. It works pretty good except that the image is upside down. It takes some getting used to. Ha. Otherwise the only thing left for the transit was a way to determine direction. A compass worked well for that. The transit was ready.
The only thing I had that would work for a scope was a spotting scope for a telescope. I mounted it in the uprights. It works pretty good except that the image is upside down. It takes some getting used to. Ha. Otherwise the only thing left for the transit was a way to determine direction. A compass worked well for that. The transit was ready.
STEP 3: Going to Work...
To use the transit you start by placing the tripod on a fairly level space. If necessary you may have to raise or lower a leg or two to compensate for uneven ground. With the transit solid on the tripod and fairly level use the three eybolts to adjust the transit so your measurements are taken properly. Direction is determined by the compass.
A measuring pole can be made from a long pipe or board. I made a 11’ pole by ripping a scrap 2x4 and splicing it together. For the measurement I tacked an old tape measure on it. Then I made a slide so my helper could mark the measurement with the slide if I cannot see the numbers on the rule clearly. The pole turned out a bit heavy so I’ll probably make a shorter one with something lighter.
Using a transit requires a rudimentary understanding of grades, compass direction and measurement. With a bit of patience and work you can plot out the grade of a piece of land accurate enough to determine drainage or how much effort it will take to level the property. Sure saves a lot of money on surveyors and equipment!
Comments
lawrencrj 11 years ago
The short coming of this design (in my opinion) is that it seems that you need to set it to level after it changes direction because you only have one level indicator on your leveling board -- so if you turn the platform to a 90 degree direction from a direction in which the scope was level, it could be (and probably WOULD be) out of level in the new direction you are shooting and would need to be leveled again.
So instead of having the two boards that hold the scope mounted directly to the leveling board it might better be attached to another rectangular board that pivots on a shaft that is "exactly" perpendicular to the leveling board. ( A pipe flange with a short nipple screwed into it should serve the purpose. The mounting board would need to be thick enough so that using a drill press the hole bored perpendicular through it would not have much play. The hole should be drilled with an adjustable bit so that it's only slightly larger in diameter than the pipe nipple it rotates on. You would want enough friction between the wood and the nipple so that the scope assembly would stay put wherever you turn it to but not enough to make it hard to turn. The leveling board would need two levels perpendicular to each other rather than a single level. Perhaps a couple little line levels that you would calibrate while the leveling board were placed on a level table. It would be a little tricky to level with three leveling bolts and two levels at right angles, so a single round (bulls eye) bubble level would be a better choice if you are going to have three leveling bolts rather than four. (Four leveling screws has problems of its own, so three with a round bubble level would be better choice.)
Your use of the dome shaped fixture was very clever and what I liked best about your design. I plan on using your idea to build my own with the "improvements" I suggested. I think I will use my little flash light that has a red laser beam rather than a scope and use it on a cloudy day or at dusk, so that the laser beam on the pole will be easier to see.
BTW -- a simple way to see if two points are on the same level is to use a long water hose filled with water. lower the high end very slowly while keeping the water from running out the stationary end. When the water starts running out the end, then it is at the same level as the end you are holding. Air pressure will keep much water from running out the end you are lowering, so you need to intermittantly let air into the stationary end as you lower the far end of the hose you should have a bottle of water to keep the hose full when the two ends are close to level. When both ends are at the same level and filled with water you will see the water about a half inch or less from the opening of the hose. As you pour a little water into one end it will flow out the other end in the same volume you added (and with a surprisingly short time lag.) This has the advantage of not requiring a line of sight when there are obstacles like trees or brush between the two points. It is a much slower process than using a transit -- but you don't have to build anything tp get an error of no more than an inch.