In Star Trek it is frequently seen that when a crew member wants to avoid being tracked, they'll leave their communicator somewhere (quarters, corridor etc) which throws the computer and ship's security off their trail.

However, the entire interior of the ship is under constant surveillance by the internal sensors. Barring damage to the ship or sensors, or some space phenomenon causing radiation X to create interference, why aren't these internal sensors able to continue tracking every person on board regardless of where their comm-badge is? In the worst case, they should be able deduce who the errant individual is by simple subtraction: "I can see where all the other comm-badges are, so subtract them and the remaining life form must be the person I am looking for." But this never seems to be done either.

Is Star Fleet security really so inept or is there some other limitation in play that is never mentioned?

  • 1
    Privacy laws...
    – AncientSwordRage
    Commented Oct 21, 2012 at 17:51
  • Because other people walk around the shop without their communicators on
    – Valorum
    Commented Feb 12 at 18:23
  • Tracking by comm badge works in the 99.999% normal situation. Most people do not leave their badge behind. Star Fleet works under the impression that their crews are the "good guys" and aren't going to be intentionally trying to defeat tracking.
    – FreeMan
    Commented Feb 12 at 18:41
  • They have on multiple occasions tracked an individual across the surface of a planet using "life signs." It seems like the same technology could be used on the ship. Commented Feb 12 at 19:08

2 Answers 2


Internal sensors have been used like that several times:

  • ENT 4x09, Kir'Shara, Lieutenant Reed tried and was unable to locate the Vulcan bio-signs of Soval.
  • TNG 5x06, The Game, when the affected crew find Wesley Crusher by tracking the heat signature from his body.
  • TNG 7x15, Lower Decks, one of the ensigns used internal sensors to find a lost puppy.

Additionally, not everyone is going to have a combadge - Federation combadges are for Starfleet personnel only (Bajorans have their own design), which makes tracking someone without one a lot more difficult. Especially on Deep Space Nine, where the vast majority of the inhabitants don't have their own combadges.


Using Federation technology (and likely the same with other Alpha Quadrant majority factions) it is well with the capabilities to track every individual on a ship or space station with or without a communications badge. Comm badges are tracked because their goal is to provide an emergency lock-on in case of medical emergency or a need for immediate transport as well as a communications support device.

  • Ship's sensors have been able to determine the quantity, location, weaponry on board a ship even before it is boarded. This capacity is used by Klingon boarding parties to best determine where to strike an enemy ship once its shields are down.

  • This same capacity is easily turned inward if necessary, to determine when enemy units may be onboard your ship and the best way to use internal defenses to prevent or limit their movement.

  • When the Federation decides they need to track or reverse engineer a particular person from a crowd they are easily able to do so with an alarming degree of accuracy. If they have access to the medical records of a crew member, any particular irregularities can be used as sorting data to eliminate other personnel from the search.

  • It is not a failure of Alpha Quadrant technology that prevents them from being able to track people without a comm badge, it is the freedom ethos that the Federation promotes which prevents them from outright tracking every individual all of the time. The Federation wants its citizens to NOT feel as if they are part of a "surveillance state."

In places where such personal freedoms may not exist, such as the Romulan Star Empire, it is possible or even likely that constant surveillance takes place wherever the government may feel it is necessary.

  • 2
    I'm not sure the second bullet is correct - internal sensors are separate from external sensors. And offhand, I don't recall the third bullet ever happening, do you have a reference? (I know they can pick out species easily, that happens a lot, but specific biological irregularities I don't recall) I do agree with the 4th bullet, though, with an example of the "privacy" aspect being Sisko's father during the blood testing.
    – Izkata
    Commented Oct 21, 2012 at 23:14
  • The systems are separate, but the technology is exactly the same. I will have to hunt through TOS but there was an episode where they use the internal sensors to determine a murderer was still onboard the ship after removing all of the active heartbeats of the crew remaining on the ship. Commented Oct 21, 2012 at 23:22
  • That would be Court Martial, which I did forget about. But they did help it along it by removing (almost) all the crew from the Enterprise, so there were only something like 15 heartbeats in total, and had to record the heartbeats of the people left onboard - the sensors couldn't do it automatically.
    – Izkata
    Commented Oct 21, 2012 at 23:24
  • The internal sensors were used to locate Wesley Crusher when he was the only crew member, besides Data, unharmed by the game Riker brought back from Risa. The sensors were able to locate him, despite him not having his combadge on, by registering him as an unidentified heat source. (TNG: "The Game") Commented Oct 21, 2012 at 23:25
  • They scanned for Crusher's body heat in a specific section of the ship to find his exact location - still not biological irregularities...
    – Izkata
    Commented Oct 21, 2012 at 23:26

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