What specifies the accuracy of measurements on a GNSS device?

The accuracy of measurements on a GNSS (Global Navigation Satellite System) device is fundamentally determined by the manufacturer's specifications. These specifications provide critical information regarding the performance capabilities of the device, including the expected accuracy under ideal operating conditions, the types of satellites it can access, and the technology used (such as single-frequency or dual-frequency reception).

While the observer's experience can influence how effectively a GNSS device is used – for instance, knowing how to mitigate errors or optimize measurement conditions – the inherent accuracy is still reliant on the device's specifications. Similarly, environmental settings, such as atmospheric conditions or physical obstructions, can affect performance but do not define the device's base accuracy.

Thus, the manufacturer's specifications stand as the primary reference for understanding a GNSS device's accuracy, making it the most direct and valid answer in this case. Other factors may play a role in the overall measurement process, but they do not specify the accuracy in the same definitive manner.