‘Inertial measurement equipment or systems’, having any of the following: Notes: 1. ‘Inertial measurement equipment or systems’ incorporate accelerometers or gyroscopes to measure changes in velocity and orientation in order to determine or maintain heading or position without requiring an external reference once aligned. ‘Inertial measurement equipment or systems’ include: — Attitude and Heading Reference Systems (AHRSs); — Gyrocompasses; — Inertial Measurement Units (IMUs); — Inertial Navigation Systems (INSs); — Inertial Reference Systems (IRSs); — Inertial Reference Units (IRUs). 2. This paragraph does not apply to ‘inertial measurement equipment or systems’ which are certified for use on ‘civil aircraft’ by civil aviation authorities of one or more Member States. (a) Designed for ‘aircraft’, land vehicles or vessels, providing position without the use of ‘positional aiding references’, and having any of the following ‘accuracies’ subsequent to normal alignment: 1. 0,8 nautical miles per hour (nm/hr) ‘Circular Error Probable’ (‘CEP’) rate or less (better); 2. 0,5 % distanced travelled ‘CEP’ or less (better); or 3. Total drift of 1 nautical mile ‘CEP’ or less (better) in a 24 hr period; (b) Designed for ‘aircraft’, land vehicles or vessels, with an embedded ‘positional aiding reference’ and providing position after loss of all ‘positional aiding references’ for a period of up to 4 minutes, having an ‘accuracy’ of less (better) than 10 metres ‘CEP’; (c) Designed for ‘aircraft’, land vehicles or vessels, providing heading or True North determination and having any of the following: 1. A maximum operating angular rate less (lower) than 500 deg/s and a heading ‘accuracy’ without the use of ‘positional aiding references’ equal to or less (better) than 0,07 deg sec(Lat) (equivalent to 6 arc minutes rms at 45 degrees latitude); or 2. A maximum operating angular rate equal to or greater (higher) than 500 deg/s and a heading ‘accuracy’ without the use of ‘positional aiding references’ equal to or less (better) than 0,2 deg sec (Lat) (equivalent to 17 arc minutes rms at 45 degrees latitude); (d) Providing acceleration measurements or angular rate measurements, in more than one dimension, and having any of the following: 1. Performance specified for accelerometers and gyros described above along any axis, without the use of any aiding references; or 2. Being ‘space-qualified’ and providing angular rate measurements having an ‘angle random walk’ along any axis of less (better) than or equal to 0,1 degree per square root hour.