The Prime Power Unit (PPU) is an air- and highway-transportable, trailer-mounted 1.3MW (megawatt) Generator Set, a key component of the Terminal High Altitude Air Defense (THAAD) system.

主动力单元（PPU）是一种可搭载空中和公路运输，拖车式1.3MW （兆瓦）发电机组，这也是终端高空防御系统（THAAD）的关键组成部分。

youdao

The Global Positioning System enables properly equipped users to determine precise time and velocity and worldwide latitude, longitude and altitude to within a few meters.

GPS允许持有对应设备的用户来确定精确的时间、速度、经纬度以及海拔，而误差只有几米。

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13 p.m. - Messages report more problems: The system that monitors speed, altitude and direction failed.

11点13分——讯息显示更多的问题：监测速度、高度和方向的仪表失灵。

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Alongside the HTC-made handset are an altitude and orbit control system, two propulsion setups and a Linux-based computer with a "high-speed" processor.

ENGADGET

And what - we can't leave out the terminal phase of missile defense, which is things like PAC-3, the Patriot Missile System, and the Terminal High Altitude Area Defense or THAAD, which would shoot down on a threat missile in the final phase of its flight.

NPR: Missile Defense, the U.S. and Europe

To combat this threat, aircraft have a warning system which alerts the crew if the cabin altitude is approaching dangerous levels.

BBC: NEWS | Europe | Dangers of aircraft decompression