What is the primary cause of systematic errors in surveying?

The primary cause of systematic errors in surveying is indeed related to instrument calibration issues. These systematic errors occur consistently under the same conditions and are typically due to flaws in the measuring instruments or techniques used. If a surveying instrument is not properly calibrated, it can produce measurements that are consistently inaccurate in the same direction—either too high or too low.

For example, if a leveling instrument is miscalibrated, it might always read a certain height incorrectly. This leads to errors that can be accounted for and corrected, but the nature of systematic errors makes them different from random errors, which are more unpredictable and vary from one measurement to another.

While observer mistakes, random factors, and environmental conditions can introduce errors into surveying measurements, they do not typically manifest as systematic errors. Observer mistakes can lead to random errors, and environmental conditions may cause variations in readings that are not consistently repeatable. Hence, calibration issues are the root cause of systematic errors because they introduce a consistent bias into the measurements taken.