head mounted displays (HMD), namely, head or helmet mounted optical displays; head mounted display systems (HMD systems) comprising HMD and built-in or external hardware for generating data to be displayed on HMD; inertial measurement units (IMU) comprising accelerometers and gyroscopes for measuring and reporting attitude, position, movement, velocity, angle, orientation and gravitational forces; goggles comprising HMD, HMD systems, HUD, HUD systems or IMU; software applications, namely, desktop and web applications for displaying and overlaying on maps data downloaded from HMD, HMD systems, HUD, HUD systems or IMU and for processing, filtering, sharing or manipulating such data; smartphone applications and mobile phone applications for adding functionalities to HMD, HMD systems, HUD, HUD systems or IMU and for storing and displaying data from HMD, HMD systems, HUD, HUD systems or IMU; computer software platforms for developing desktop and web applications, mobile phone applications and smartphone applications for use in association with HMD, HMD systems, HUD, HUD systems or IMU