Short Answer:

Systematic errors in surveying are the types of errors that occur in a regular and predictable pattern. They usually happen due to imperfections in instruments, incorrect settings, or environmental conditions like temperature or wind. These errors repeat in the same way every time under the same conditions.

Unlike random errors, systematic errors can be identified and corrected if the source is known. Surveyors apply correction formulas or calibration to reduce their impact and ensure that the final survey results remain accurate and trustworthy.

Detailed Explanation:

Systematic errors in surveying

Systematic errors in surveying are errors that occur repeatedly in the same way whenever the same conditions are present. These are not accidental or unexpected errors but rather errors that follow a consistent pattern. Because of their predictable nature, systematic errors can be detected, measured, and corrected to improve the accuracy of the survey results.

Surveying involves measuring distances, angles, and elevations using various instruments like total stations, theodolites, levels, and chains. If these instruments are not perfectly adjusted, or if the environment causes slight variations, systematic errors can affect every reading in the same direction—either too high or too low.

Causes of systematic errors

1. Instrumental errors
   These errors are caused by flaws or misadjustments in the instrument. Examples:
   • An incorrectly calibrated level bubble
   • A total station with a misaligned telescope
   • A tape that has stretched over time
2. Natural or environmental errors
   These are caused by environmental conditions such as:
   • Temperature changes causing tape expansion or contraction
   • Wind affecting plumb bob alignment
   • Refraction and curvature affecting long-distance leveling
3. Personal or human errors
   These happen when surveyors use instruments in a consistent but incorrect way, such as:
   • Always reading the wrong edge of a tape
   • Holding a leveling staff at an angle instead of vertically

Even though these errors originate from different sources, their effect is repeatable and can therefore be adjusted for.

Examples of systematic errors

• Tape measurement error due to temperature: A steel tape expands in hot weather, so the measured length may be longer than the actual ground length.
• Leveling error due to instrument misleveling: If the level is not adjusted correctly, all readings will shift in the same direction.
• Refraction and earth’s curvature: In long sight lines, the curvature of the earth and the bending of light rays can cause consistent elevation errors if not corrected.

How to reduce or eliminate systematic errors

1. Calibration: Instruments should be regularly checked and calibrated before use.
2. Standard procedures: Following proper survey methods and steps can avoid human mistakes.
3. Environmental corrections: Apply standard correction formulas for temperature, pressure, and slope.
4. Use of standard tools: Certified and well-maintained instruments help reduce chances of system-based mistakes.
5. Double-checking measurements: Taking measurements in reverse or from both directions can help identify if a consistent error exists.

Understanding systematic errors allows surveyors to apply corrections to their observations, improving the final result’s reliability. Many instruments come with built-in compensation functions that automatically apply such corrections.

Conclusion:

Systematic errors in surveying are repeatable and predictable mistakes caused by faulty instruments, environmental effects, or consistent human error. Since they follow a fixed pattern, surveyors can detect and correct them to ensure the accuracy of survey work. Proper equipment care, field checks, and correction formulas are key to reducing their impact and ensuring trustworthy measurements.