1. Remove your dumpy level’s lens cap. The lens cap protects your device’s lens from unwanted dirt, grime, and debris. To avoid damaging your instrument, leave the lens cap on until you’re ready to use the device.[7]
If your lens is dirty, wipe it down with a pre-moistened lens wipe. You can find these at most camera stores and a number of big-box stores.
2. Adjust the eyepiece until you can see the device’s crosshairs. Place a sheet of paper or a similar object directly in front of your device’s lens to occupy its entire field of vision. Then, turn the eyepiece’s focusing knob until you can clearly see the dumpy level’s crosshairs.[8]
When finished, your crosshairs should appear dark, sharp, and easily noticeable.
3. Twist the device’s focusing knob until the image is clear. Once you can see the crosshairs, point your device’s telescope toward your benchmark spot. Look for a large, distinct object in the area, such as a tree or hilltop, then twist your device’s primary focusing knob until the object comes into focus.[9]
If you’re having trouble focusing, ask a friend or colleague to hold an E staff near the benchmark spot. This metered measuring stick will give you an easy object to focus on.
Part 3: Taking a Measurement
1. Position an E staff on top of your benchmark spot. If necessary, purchase an E staff online or from a survey equipment shop. Then, have a friend or colleague hold the staff on top of your benchmark spot.[10]
For the most accurate measurements, have your friend rock the staff forwards and backwards and record the lowest number you read.
Most E staffs collapse to save space, so make sure you extend your staff before taking any measurements.
Use a fiberglass staff instead of a metal version if you’re taking measurements in an area beneath power lines.
2. Find the height difference between your level and the benchmark spot. Look through your dumpy level’s telescope and locate the E staff. Then, record the measurement indicated by your device’s center, horizontal crosshair.[11]
This measurement is known as your backsight.
Each numbered section of your staff represents 10 cm (3.9 in). Within these sections, every block indicates 1 cm (0.39 in) and every E indicates 5 cm (2.0 in).
3. Calculate your level’s actual height using the benchmark height. Once you have your backsight measurement, add it to your benchmark location's actual height. This will give you the current height of your dumpy level’s telescope.[12]
Record this measurement so you can use it to find the height of your next spot.
4. Find the height difference between your level and the unmeasured spot. Move your E staff so it sits directly on top of the spot you want to measure. Use your device’s telescope to find the staff, then record whatever number the device’s center, horizontal cross hair sits over.[13]
This measurement is known as your foresight.
If necessary, adjust your eyepiece’s focusing knob until you can see the staff.
If the spot is too high or far away for you to measure, move your staff to a lower, closer spot first. Find the height of this new spot, then move your dumpy level to it and restart the measuring process.
5. Calculate the spot’s actual height using your level’s height. Unlike with your previous calculation, you’ll need to subtract your foresight measurement from your dumpy level’s actual height. This will give you the height of the spot you measured.
When your record this height, make sure to include a thorough description or diagram of the spot you measured. That way, if you return to the area, you’ll be able to find the measured spot easily.
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