v\Precision in GNSS positioning describes the consistency, repeatability, or clustering of position measurements under unchanged conditions, how closely repeated observations agree with each other, independent of whether they match the true position. This statistical concept is distinct from accuracy (closeness to truth) and represents an essential quality metric for understanding positioning system performance and reliability.
High precision indicates that a positioning system produces tightly grouped results when measuring the same location repeatedly or tracking a consistent trajectory. The system’s outputs cluster within a small area, demonstrating low random variability and stable performance. Precision is typically quantified using statistical measures like standard deviation, root mean square (RMS), or confidence ellipse dimensions, often reported as CEP (Circular Error Probable) or values at 68% and 95% confidence levels.
The relationship between precision and accuracy is frequently misunderstood. A system can be highly precise but inaccurate, consistently reporting positions that cluster tightly around a point offset from truth. Conversely, a system can be accurate on average but imprecise, producing measurements that scatter widely but center on the true position. For most applications, both high precision and high accuracy are desired, though their relative importance varies by use case.
For certain applications, precision may actually matter more than absolute accuracy. Lane-keeping and path-following functions in autonomous vehicles require repeatable positioning to maintain consistent trajectories, even if absolute position has some offset. Relative positioning between vehicles for platooning depends on precision rather than absolute accuracy. Deformation monitoring detects changes by comparing precise measurements over time. Understanding the distinction between precision and accuracy enables proper specification of positioning requirements and appropriate interpretation of system performance data.
