About Lesson
Errors in Surveying
- Discrepancy: Difference between two measured values of the same quantity.
- Error: Difference between a measured value and its true value.
Types of Errors
- Mistakes (Blunders)
- Caused by human carelessness or poor judgment.
Examples:
- Transposing numbers.
- Misreading instruments.
- Incorrect backsight/foresight point.
Prevention: Stay alert, use common sense, double-check entries.
- Systematic Errors
- Consistent in magnitude and direction under same conditions.
- Follow physical/mathematical laws.
Examples:
- Tape expansion due to temperature.
- Incorrect instrument calibration.
- Curvature and refraction errors.
Solution: Apply standard corrections or follow proper procedures.
- Random Errors (Accidental)
- Unpredictable, obey laws of probability.
- Caused by factors like parallax, observation habits.
- Tend to cancel out over multiple observations.
Solution: Minimized by repeating measurements and using averages.
Sources of Errors
a) Personal Errors
- Due to observer’s limitations (e.g., eyesight, fatigue).
- Can be systematic or random.
b) Instrumental Errors
- Due to imperfect instruments (e.g., faulty calibration).
- Solution: Regular checking and instrument maintenance.
c) Natural Errors
- Due to environmental factors (e.g., temperature, wind, refraction).
- Solution: Apply environmental corrections.
Accuracy vs. Precision
|
Term |
Definition |
|
Accuracy |
Closeness to true value; indicates quality of result |
|
Precision |
Consistency in measurement technique; refers to quality of method |
Note: Accurate result = requires precise method + instrument + procedure + planning.