# Swap nose-point and tail-base

Aim

To exchange the nose-point and the tail-base within a sample (or range of), after checking that these were assigned incorrectly by EthoVision XT.

In the example below, the nose-point and the tail-base point are assigned incorrectly (left). The Swap action puts the nose-point and the tail-base point back in the correct place.

To check that nose-point and tail-base were mistakenly exchanged, choose Analysis > Results > Integrated Visualization. Play back the tracks with the video on the background. Check that the nose-point and tail-base do correspond to the actual orientation of the subject.

Procedure

Choose Acquisition > Edit Tracks.

Choose one of the two options:

▪Swap nose-point and tail-base point manually. Look for the samples with exchanged nose-point and tail-base, and give the Swap command for those samples.

▪Swap nose-point and tail-base point automatically. Define a criterion for automatic detection of changes in orientation of the nose-point and tail-base. EthoVision XT searches your tracks for the samples where a sudden change in orientation has occurred. It is up to you to swap nose-point and tail-base for those samples.

Notes

▪By selecting the tracking methods Rodents / For occlusions or Adult Fish / For occlusions, you can minimize the occurrence of nose-tail swaps. However, this method requires much processor load, so make sure you do not miss samples.

▪If a large number of samples contain wrongly-assigned nose-point and tail-base, it may mean that the detection settings for nose-point and tail-base detection are not optimal, or that you need to improve the lighting or other settings of your setup.

▪You can click Save on the toolbar so that if you are editing many swaps and make a mistake, you do not loose your edits.

▪When you swap nose- ant tail-base points, the Head direction line is recalculated too. This influences the calculation of Head direction, Head directed to zone and Turn angle and Angular velocity when they are based on Head direction.