The Pocket Radar products are all based on newer technology than the traditional large radar guns. They are very stable and holds the factory calibration. It does NOT require further calibration.You can verify the calibration using a special Pocket Radar Calibrated Tuning Fork.  This Tuning Fork is provided with the professional traffic engineering model, the Traffic Advisor. If you would like to purchase a Calibrated Tuning Fork for use with another model of Pocket Radarhttps://www.pocketradar.com/products/calibrated-tuning-fork-for-accuracy-verification