How does the HoloLens keep holograms in place?

All HoloLens use inside-out tracking to calculate the changes in the position of your headset as you move around in your physical environment. Inside-out tracking works by using the four grey-scale cameras on the HoloLens to observe features (points of high contrast) in your environment, and triangulates the position of your head by determining the offset of these features in each camera. This position is combined with data from the inertial motion unit (IMU) that provides accurate measurements of the roll, pitch and yaw of the headset.

There are a number of actions you can take to improve the accuracy of your holograms, as outline here: Best Practice