A GPS receiver whose principal function is navigation — determining position, course, or speed — generally falls under heading 9014. A module integrated into a communication device or sold primarily as a wireless communication component may instead classify under the telecommunications heading. The essential-character test and the relevant section notes govern borderline cases.

Subheading 901420 covers instruments and appliances specifically designed for aeronautical or space navigation, such as altimeters, air-speed indicators, and inertial reference units certified for aircraft use. Instruments designed for marine, land, or general-purpose navigation that are not specifically aeronautical fall under 901480. Certification standards and design specifications are the practical distinguishing factors.