Tapes are used in surveying to measure horizontal, vertical, and slope distances. They may be made of a ribbon or a band of steel, an alloy of steel, cloth reinforced with metal, or synthetic materials. Tapes are issued in various lengths and widths and graduated in a variety of ways.
Types of Measuring Tape Used in Survey
Surveying tapes are made of various materials and therefore can be divided into different types as follows.
1- Linen Tape
Linen tape, also known as cloth tape is a varnished strip made of closely woven linen. The width of the strip is about 12 to 16 mm. It is available in different lengths such as 10m, 20m, 30m, and 50m. Both ends of the linen tape are provided with metallic handles and the whole tape is wounded in leather or metal case. Linen tapes are light in weight and easy to handle. These tapes may shrink when exposed to water and also elongate when pulled. Hence, these tapes are not suitable for accurate surveying measurements. These are generally used for plumbing offsets and for ordinary works.
2- Woven Metallic Tape
The metallic woven tape is an improved version of linen tape. Brass or copper made wires are used as reinforcement for the linen material. Hence, it is more durable than normal linen tape. A brass ring is provided at the end of the tape which is included in the length of the tape. These tapes are available in different lengths of 2m, 10m, 15m, 20m, 30m, and 50m. These are used for survey works such as topographical survey works where minor errors are not taken into consideration.
3- Steel Tape
A steel tape is made of steel or stainless steel. It consists of a steel strip of 6mm to 16mm wide. It is available in lengths of 1m, 5m, 8m, 10m, 20m, 30m and 50m. Meters, decimeters, and centimetres are graduated in the steel strip. Steel tapes generally came up with the metal case with automatic winding device. The tape is withdrawn from the case by using a hand during measuring and it is rewound into the case by just pressing button provided on the case. Steel tapes are not flexible and are suitable for measuring levelled surfaces only. They may corrode easily when exposed to moisture and to prevent this tape, it should be cleaned and oiled after every use. These tapes are generally used for standardizing chains, measurements of constriction works, etc.
4- Synthetic Tape
Synthetic tapes are made of glass fibres coated with PVC. These are light in weight and flexible. They are available in lengths of 5m, 10m, 20m, 30m, and 50m. Synthetic tapes may stretch when subjected to tension. Hence, these are not suitable for accurate surveying works. However, synthetic tapes are recommended in place of steel tapes where it is essential to take measurements in the vicinity of electric fences and railway lines, etc.
5- Invar Tape
Invar tapes are made of an alloy which consists of 36% of nickel and 64% of steel. Invar tape contains a 6mm wide strip and is available in different lengths of 30m, 50m, 100m. The coefficient of thermal expansion of invar alloy is very low. It is not affected by changes in temperature. Hence, these tapes are used for high precision works in surveying such as baseline measurement, triangulation surveys, etc. Invar tapes are expensive than all the other types of tapes. These tapes should be handled with care otherwise bends or kinks may be formed.