Even with the high tech Global Positioning System, (GPS) equipment, surveyors still use steel measuring tapes for linear distance between two points. Measuring distances with steel tape began early in the twentieth century. Survey tapes are metal and commonly 100 feet long, but available in other lengths. Tapes are graduated in feet and tenths of a foot. When used properly, the best steel tapes give reliable, accurate measurements. Steel tape measuring is possible to achieve accuracy of 1 foot in 5000 feet to 1 foot in 10,000 feet. Training and taking land survey courses are needed for this profession.
Identify Points A and B
Identify point A and Point B to be measured with a steel or fiberglass tape. Point A is a known point and point B is an unknown point. Point A could be a survey marker, the corner of a building or a natural feature. A red and white striped range pole can define point B.
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The front person takes the zero end of the tape with the spring tensioner, a spring scale that measures the pull tension on the tape in pounds, and pulls it toward point B. The rear person will call “tape” when the steel tape comes off the reel. Then, with hand signals, the rear tape person aligns the front person with point B.Credit: Public domain courtesy NOAA library.
Applying Tension and Leveling
After aligning the tape between points A and B, the front person will pull the steel tape measure until the spring tension is approximately 10 pounds to minimize sag in the tape. He may use a level to make certain the tape is level. The back person uses a metal clamp to hold the tape. It looks somewhat like scissors without the blades. Put the tape through the slot at the hinged area and it clamps down to hold the tape when it’s pulled.
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The front person uses a taping pin, a red and white striped heavy gage wire with a finger loop on one end and sharp on the other end to mark the tip of the plumb bob. He pushes it in the ground at a 45-degree angle at the point of the plumb bob tip.
Survey tapes are marked in foot increments after the second foot. If the distance is a full tape length, the readings will be at the zero and 100-foot readings. If the reading is less than a 100 feet, the back person moves forward to the closest foot marker to the pin. The front person will slide his string along the tape until it is over the point and note the fractional portion of a foot. A survey tape has graduations marked in fractions of a foot at the zero end on both sides of the zero mark. Graduations on both sides allow recording the distance more or less than a foot.
Record and Check Distance
Record the distance with a pencil on a tablet. Check by counting pins. The front person will start with 10 and the back person 1. If they have taped 350 feet, the front person will have 6 and the back person will have 4 and the last 1 is in the ground. Record the temperature at the beginning and end of the process. The steel tape will expand in hot weather, and contract in cold. The temperature to calibrate the tape is 68 degrees, and an expansion or contraction factor will compensate for the temperature difference. Someone other than the taping crew will make the decision to calculate for temperature compensation.
If a slope is too steep for the tape to align parallel with the flat ground, the measurements are in portions of a tape. Align one end with the pin in the ground. The other tape person will make measurements with the tape no higher than shoulder high.
Precautions and Maintenance
There are several precautions to take while taping. It is a good idea to make a sketch of the taping route. Wait until the plumb bob is still before marking the point. When reeling the tape back on its reel, use a cloth with a little oil to clean the tape. Take care not to kink the tape as a steel tape can kink and break. Be aware of hazardous terrain, animals, snakes and vegetation in the area.
Steel tape measures are used for home property survey, property line survey and any other survey that requires a distance measurement. Survey crews still use steel tape measures, even in the era of high tech electronic survey .