Knowledge Base

Problem

After acquiring trials, a user discovers the calibration line was set incorrectly (e.g., the software did not allow saving the correct calibration, or a wrong value was used). The user wants to delete or replace the calibration line but cannot find a way to do so within EthoVision.

Details

Symptom: No option exists to edit, delete, or replace the calibration line after trials have been recorded. All derived measurements (distance, velocity, zone area) are based on the incorrect calibration. Affected: All EthoVision XT versions. Calibration is locked as part of the Arena Settings once acquisition has occurred.

Solution

1. Understand that it is not possible to edit, delete, or replace a calibration line after a trial has been acquired in EthoVision XT. Calibration is fixed at the time of acquisition and all positional data is calculated from it.
2. If the calibration error is minor, consider applying a manual correction factor outside of EthoVision (e.g., in Excel) by multiplying exported distance/velocity values by the ratio of the correct calibration to the incorrect one.
3. For future experiments, always verify the calibration line before starting acquisition: use a known physical reference (e.g., a ruler or the Noldus calibration card) placed flat in the arena at the same plane as the animal.
4. If the experiment has not yet started, you can still correct the calibration in Arena Settings before the first trial.
5. Contact Noldus Support if you need advice on post-hoc data correction strategies for your specific experimental setup.