What did the Adsid sensor look like?

Short answer

The ADSID was a seismic sensor: an internal geophone detected vertical ground movement and could tell a man from a vehicle moving at 33 and 109 yards (30 and 100 m). The system's sensors were air-dropped, by parachute, which hung them in trees, or by gravity, which planted them in the ground like a dart. In 1972 dollars it cost $619.

Published: November 1, 2026 · Updated: November 1, 2026 · Edited by Above Ten Thousand · Editorial policy

General Atomics MQ-1L Predator A

A stake driven in from the air

The sensors were designed for air deployment in two ways: by parachute, which left them hanging in trees looking like foliage, and by gravity, which drove the stake-shaped device into the ground like a lawn dart and buried it except for the antennas, designed to look like weeds. The camouflaged sensors were to be dropped in strings over predetermined geographic points of the PAVN logistics network.

Geophone and detection range

The ADSID detected vertical ground movement by means of an internal geophone. It could determine whether what was moving was a man or a vehicle at 33 and 109 yards (30 and 100 m) respectively. The system's first acoustic sensors came from the US Navy's Project Jezebel anti-submarine sonobuoys, which recorded and processed sound by means of an audio spectrum analyser.

Cost and close relatives

In 1972 dollars, the ADSID cost $619.00. The ACOUSID, short for Acoustic Seismic Intrusion Detector, combined the operation of seismic and acoustic devices and added the ability to transmit sound from a built-in microphone. That model cost $1,452.00 in 1972 dollars. Information from the sensors reached the computers of the Intelligence Collection Center in Thailand, which collated it and predicted convoy routes and speeds.