Engineers use profilometers to measure the texture and roughness of a surface, which is critical for parts that experience friction, like engine pistons. 2. Interchangeability and Mass Production

: Focuses on developing new measurement methods and maintaining primary units like the SI Units (e.g., length, mass, time).

In the pre-industrial era, parts were hand-filed to fit one specific machine. If a part broke, a craftsman had to fabricate a new one from scratch. Metrology introduced the concept of tolerances and limits. By defining exactly how much deviation from a nominal dimension is acceptable (e.g., $50mm \pm 0.05mm$), engineers enabled mass production.

In civil engineering, the scope involves large-scale surveying and alignment. Laser trackers and theodolites measure distances spanning kilometers to ensure bridge segments align or tunnel boring machines meet precisely underground. Here, environmental factors like temperature and gravity play a massive role in measurement accuracy.

Focused on real-time control during manufacturing.