In surveying, tapes are essential tools used to take precise linear measurements. These tapes are made from various materials, come in different lengths, and serve a wide range of surveying tasks. This article delves into the five most common types of tapes used in surveying, highlighting their features, advantages, limitations, and applications.
1. Linen Tape
Linen tape, commonly referred to as cloth tape, is crafted from closely woven linen that is varnished for durability. These tapes are typically 12-16 mm wide and are available in lengths of 10m, 20m, 30m, and 50m. Metallic handles are affixed to both ends, and the tape is wound into a leather or metal case for storage.
Advantages:
- Linen tapes are lightweight and easy to handle, making them a practical choice for general tasks.
Limitations:
- These tapes tend to shrink when exposed to water and elongate under tension, making them unsuitable for precise measurements.
Applications:
- Linen tapes are commonly used for measuring offsets and other basic surveying activities.
2. Woven Metallic Tape
An improved version of the linen tape, woven metallic tape incorporates brass or copper wires into its structure for added reinforcement and durability. It includes a brass ring at one end, which is factored into the tape’s length. These tapes come in lengths of 2m, 10m, 15m, 20m, 30m, and 50m.
Advantages:
- More durable than plain linen tapes due to the metallic reinforcement.
Applications:
- Ideal for topographical surveys and other tasks where minor measurement errors are acceptable.
3. Steel Tape
Steel tapes are made of steel or stainless steel, with widths ranging from 6mm to 16mm. Graduated in meters, decimeters, and centimeters, these tapes come in lengths of 1m, 5m, 8m, 10m, 20m, 30m, and 50m. They are stored in a metal case equipped with an automatic winding mechanism.
Advantages:
- High accuracy, especially when used on leveled surfaces.
Limitations:
- Steel tapes are prone to corrosion when exposed to moisture. To maintain their longevity, they must be cleaned and oiled after use.
- They lack flexibility, which can limit their usability in uneven terrains.
Applications:
- These tapes are commonly used for standardizing chains and in construction measurements.
4. Synthetic Tape
Synthetic tapes are manufactured from glass fibers coated with PVC, making them lightweight and highly flexible. These tapes are available in lengths of 5m, 10m, 20m, 30m, and 50m.
Advantages:
- Synthetic tapes are a practical alternative to steel tapes in environments with electric interference, such as near electric fences or railway lines.
Limitations:
- These tapes may stretch when subjected to tension, reducing their suitability for high-accuracy surveying tasks.
Applications:
- Ideal for use in locations where metal tapes may pose safety risks or practical challenges.
5. Invar Tape
Invar tapes are composed of an alloy made from 36% nickel and 64% steel. These tapes are typically 6mm wide and are available in lengths of 30m, 50m, and 100m. The unique properties of the invar alloy make it particularly suited for precise measurements.
Advantages:
- The coefficient of thermal expansion of invar is exceptionally low, making these tapes resistant to temperature changes. This ensures consistent accuracy regardless of environmental conditions.
Limitations:
- Invar tapes are more expensive than other tape types and require careful handling to avoid damage such as bends or kinks.
Applications:
- Primarily used for high-precision tasks such as baseline measurements and triangulation surveys.
Comparison of Tape Types
| Tape Type | Material | Durability | Precision | Primary Use |
|---|---|---|---|---|
| Linen Tape | Woven linen | Moderate | Low | General measurements |
| Woven Metallic Tape | Linen with metal wires | High | Moderate | Topographical surveys |
| Steel Tape | Steel or stainless steel | High | High | Construction, standardization |
| Synthetic Tape | Glass fiber coated with PVC | Moderate | Low to Moderate | Electric-prone areas |
| Invar Tape | Nickel-steel alloy | Very High | Very High | Precision surveys |
Conclusion
Tapes play a crucial role in surveying, enabling accurate and efficient linear measurements. Each type of tape—linen, woven metallic, steel, synthetic, and invar—has unique features tailored to specific tasks and environments. Choosing the right tape depends on the requirements of the survey, the desired level of precision, and the environmental conditions. As surveying technologies evolve, these versatile tools remain fundamental to the trade, ensuring the integrity and accuracy of measurement processes.