Measurement error is an unavoidable component of the measurement process. All measurements contain a certain error component, and the surveyor's task is to minimize and control these errors to ensure results meet requirements.
Types of errors:
- Systematic errors - constant or predictable deviations
- Random errors - unpredictable variations around the mean
- Gross errors - obviously incorrect measurements
Sources of systematic errors:
- Instrumental errors - uncalibrated instruments, wear
- Methodological errors - incorrect measurement method
- Environmental errors - temperature, atmospheric pressure effects
- Personal errors - operator's systematic deviations
Sources of random errors:
- Instrument setup imprecision
- Sighting imprecision
- Reading imprecision
- Atmospheric fluctuations
Error prevention and control:
- Calibration - regular instrument verification
- Proper methodology - selection of appropriate methods
- Repeated measurements - statistical analysis
- Check measurements - verification on known points
- Adjustment - error distribution
Error propagation:
In surveying, errors combine according to specific laws:
- Systematic errors add directly
- Random errors add quadratically (√(σ₁² + σ₂² + ...))
- More measurements mean smaller total random error
Allowable errors:
- Cadastral surveying - ±5 cm (urban), ±10 cm (rural)
- Topographic surveying - 0.4mm × M (scale)
- Class III leveling - ±10mm × √L(km)
- Construction stakeout - depends on structure
Understanding error sources and control methods is essential professional surveyor competence.