Accuracy of data when communication with the cloud is lost:
When the AirTag detects no communication with the cloud it will save the data samples locally. The processing of data is still as accurate as if it were to be connected to the cloud. In other words, the same way of data processing is present regardless of the communication status.
Accuracy of data during a "no data" period caused by a loss of power:
During loss of power no data is measured, nor sent to Aircloud. The software will try to fill in the missing data by creating a line spanning the data gap. It tries to connect the last 2 incoming data points in a relatively correct way. However, in this case the line is estimated and does not reflect real data.