How to Use a Surveyor's Transit

You can find approximately where your lot lines are using a surveyor's transit and tape, hopefully a CAD program of some sort, and this procedure.


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    Get the parcel layout. You need the deed for the property, its legal description, and the map of the surrounding area. These can be obtained at the county recorder's office. The deed may specify other documents.
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    Establish control. You will want to go out to the property and find the "Point of Commencement", or POC, as described in your legal documents. Look for any lot corners and other survey evidence, both on your property and any surrounding lots that you have access to. These can take the form of "X"s chiseled in concrete (such as sidewalks or curbs); nails, in asphalt, concrete, on the tops of walls, and along street center-lines; rebar or other metal stakes in soil; or City markers, which may be found under small manhole-like covers (they should be shown on any maps of the area).
    • A metal detector is helpful for nails which often corrode and become hidden in asphalt and for stakes, which are often buried. You must find at least one of the points mentioned in the legal documents. The more, the better.
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    Establish a bearing basis. Find another control point at least a hundred yards or so from one of your found control points. The farther, the better. This point should appear on the map of the area (for example, the corner of another lot down the road).
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    Set a control mark. Find a spot where you can physically see as many of your control points as possible and the front lot corners and, if possible, the back corners that you wish to establish later (you're guessing here, but try). Mark it with a big nail, or spot of paint as appropriate. The mark must be solidly placed, so that it won't move.
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    Set up your station. Set up your transit or theodolite over the mark you set. This can be tricky. You may have a peephole at the base of the unit, or you can use a plumb bob. Set up the tripod such that the unit is directly over the mark, with the device looking more or less level.
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    Level the device. You should have two bubbles and two thumb wheels at the base of the unit. Adjust them such that both bubbles are centered. Now recheck the peephole, and adjust the position of the device by loosening the plate at the bottom and sliding the device so the mark on the ground is in the cross-hairs or under the plumb bob.
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    Backsight your bearing basis. You will need a helper with a pole. Ideally, the pole will have a bubble level so the helper can hold it upright. Also, if your instrument measures distance, it will need a prism at the top. Now, you'll need to zero the device. With the helper holding the pole, find it in the telescope. Then, unlock the angle scale and rotate it so the indicator points to 0 degrees. Electronic devices have a button for this.
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    Shoot your other points. Lock your scale, and have the helper move to each point you found. Sight the pole and write down the angle on the scale. If you can measure the distance, do so; you do not have to do this for faraway points, but it helps. If you're using a tape, make sure to pull it tight and keep it level. Both ends have to be at the same height. You can measure distances longer than the tape by marking points in between. Use the transit to place them exactly along the line between the transit and the point you are measuring.
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    Pack up. You will go do some math now, and it will take a while.
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    Prepare an analysis. You can do this with paper but a simple CAD program is much easier. Begin by plotting the theoretical position of each point you found. Start with any control point you found, and use the documentation to construct a complete map that includes your parcel and all the points you found. This map MUST be to scale!
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    Prepare data. Now, start with a new sheet of tracing paper or a new CAD layer, or just a different color. Here, you will be recreating the physical evidence. Draw a mark for the point you set earlier, and draw a line representing your backsight. Now, draw lines toward each shot you took using the first line as 0 degrees. If you have distances, you can establish exact points. If you are using CAD, group or make a block of all these lines so you can move them as one object.
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    Translate. The data will never match the map exactly, so you must pick one point to establish a starting point. Place the data over the map and see how everything matches up. If you have a marked lot corner, you should use it if the other data seems consistent. Otherwise, use your best judgment.
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    Rotate. Rotate the tracing paper or CAD block around the point you chose earlier, aligning the data to the map. You have now established the position of your control point—the spot you marked near the beginning.
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    Verify. All of the measured data should match the map now. If not, you need to find out why.
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    Calculate. Draw lines from the control point (on the data layer) to the lot corners (on the map) that you need to set. Determine their distance from the control point and their angle relative to the backsight.
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    Find your corners. Go back and set up over the control point and backsight again. Rotate the instrument to the calculated angle, and use the tape to establish the distance.
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    Mark corners. Use a spot of paint or a wooden stake. If you can't see all of the corners, set up a second control point visible from the first one. Measure it, add it to the data layer, set up your station over it, and use the first point as a backsight to set the remaining corners. Repeat as necessary.
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    Remove your control point(s). You don't want to confuse later surveyors.


  • Do not set nails, stakes, or chiseled "X"s at your corners. Later, surveyors would interpret those as properly set corners—which they are not. Use a spot of paint or a wooden stake, or some other non-permanent method.

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