# Clock Drift Expectations ROV Locator Mk II units rely on crystal oscillators to calculate slant range. Although we use low drift temperature compensated devices, there is still some difference between ROVL units that will cause slant accuracy to drift over time. Autosync units reset drift by periodically seeking a GPS time fix. You can expect similar performance to that shown below with your ROVL Mk II devices. {% hint style="info" %} Note: Mk III systems are not subject to clock drift errors. {% endhint %}

Slant range drift of two randomly-selected Mk II devices held fixed at 100 meter separation. A clock drift calibration was run about four hours prior to this test. Quantization is due to slant range being reported with one decimal place of precision (10cm resolution).

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