Consider the following example to get a feeling for the latency problem. Let be the density of the display in pixels per degree. Let be the angular velocity of the head in degrees per second. Let be the latency in seconds. Due to latency and angular velocity , the image is shifted by pixels. For example, if pixels per degree, degrees per second, and seconds, then the image is incorrectly displaced by pixels. An extremely fast head turn might be at degrees per second, which would result in a -pixel error.