Back to dictionary
General Terms
Accuracy/Precision
A measurement quality characteristic indicating how close a measurement is to the true value or the repeatability of measurements.
Precision and accuracy are two different measurement quality characteristics that are often confused. In surveying, understanding both parameters is essential for ensuring quality results.
Accuracy vs precision:
- Accuracy - how close a measurement is to the true value
- Precision - how repeatable measurements are (dispersion)
- Measurements can be precise but inaccurate (systematic error)
- Ideal measurements are both accurate and precise
Expressing precision:
- Standard deviation (σ) - statistical dispersion measure
- Root mean square error (RMS)
- Confidence interval - 68%, 95%, 99%
- Absolute error - mm, cm, m
- Relative error - ppm (parts per million)
Precision requirements in surveying:
- Cadastral surveying - ±5 cm for boundary points
- Topographic surveying - depends on scale
- Engineering geodesy - up to ±1 mm in specific works
- Deformation measurements - sub-millimeter precision
Factors affecting precision:
- Instrument quality - class and calibration
- Measurement method - method selection
- Environmental conditions - temperature, wind, visibility
- Operator skills - experience and care
- Geometry - satellite configuration, angles
Precision control:
- Repeated measurements on control points
- Traverse closure error analysis
- Comparison with higher precision data
- Statistical data analysis
Instrument precision:
- GNSS RTK - 1-3 cm horizontally, 2-5 cm vertically
- Total station - 2-5 mm + 2ppm for distances, 1-5" for angles
- Level - 0.3-3 mm/km
- LiDAR - 1-3 cm for scan points
Ensuring measurement precision is the surveyor's main task, directly affecting work quality and legal validity.