Linear measurement instruments and their permissible error range

1. Pacing

Permissible error ≤ 1 feet in 20 feet.

2. Chain

Permissible error ≤ 1 in 1000.

3. Metallic tape

Permissible error ≤ 1 in 1000.

4. Steel tape

This tape is made of steel alloy of very small co-efficient of thermal expansion.

Permissible error ≤ 1 in 1000.

5. Invar tape

This tape is made of very expensive steel alloy of almost negligible co-efficient of thermal expansion and is used for very precise linear measurements.

Permissible error ≤ 1 in 50,000.

6. Tachometry

Permissible error ≤ 1 in 50,000.

7. Electronic distance meter

Permissible error ≤ 1 in 100,000.