Radar (Radio Detection and Ranging) is a surveillance technology used heavily during the War against the GLA. As it's de-achronized name implies, radar made use of simple radio and microwave transmissions to reveal key locations to commanders allowing them to command and guide their forces with precision and efficiency. On top of this, the availability of a radar station granted commanders access to secret communication channels with their respective militaries, opening availability to special technologies and soldier divisions to support their war efforts.
Even the GLA took interest in the advantage of radar and deployed "radar vans" which were vans with small radar systems built into them. Since the GLA made minimal use of aircraft radar was not as important to them. These vans could be upgraded with additional parts the GLA often acquired from the black market to allow periodic scans of specific areas.
The USA and China's radars were dependent on external sources of electricity and would cease operation if power was cut. The GLA's radar was much simpler and could run off it's own internal power supply.