# Simulate Motion¶

Widgets -> Simulation -> Simulate Motion

This widget simulates random motion in a 4D data set. It may be useful for testing algorithms for motion correction, however the motion simulated may not be particularly realistic as it is uncorrelated and occurs randomly in all dimensions. In practice, real motion is often more prevalent in certain directions than others, and may well be correlated from one time point to another (e.g. a patient may manage to stay still for most of a long scan but then find it difficult to avoid motion the longer it goes on.

Motion standard deviation is the std.dev of the Gaussian which is used to generate random movement in each dimension. Padding adds extra voxels to the edge of the data so that motion can occur beyond the edges of the data without losing voxels. Both are specified in mm and are converted to voxels using the data voxel->world transformation matrix.