Hudson: I got signals. I got readings, in front and behind.
Frost: Where, man? I don't see shit.
Hicks: He's right. There's nothin' back here.
Hudson: Look, I'm telling ya, there's somethin' movin' and it ain't us! Tracker's off scale, man. They're all around us, man. Jesus!
Sometimes, the only way to keep track of objects is through crude sensors or motion-tracking devices. Such devices generally don't do much more than show some blips while making bleeping noises. Yet, this can sometimes amplify the tension of a scene, especially if the actual visual appearance of the objects being tracked is unknown. The closer the enemies get, the more rapid the beeping gets, until it becomes a maddeningly nerve-shredding screech that more often than not causes heroes to snap at just that wrong moment before the monsters burst through and pull them under.
A more recent usage of this trope is to have lots of blips on the radar display or to have a really big blip appear, as a precursor to something really bad happening. Alternatively, the blips might suddenly disappear, which is even worse for the heroes.
Captain! The radar shows multiple Incoming! examples!
- Gundam tends to do this by having stuff suddenly appear immediately before they come under attack. The Bridge Bunnies suddenly yelling "Heat source detected!" out of the blue usually means bad things are about to happen.
- Hanaukyō Maid Team La Verite: Episode 10. Multiple intruders are detected, and a giant screen in the security maid's HQ shows their position as they move through the mansion.
- Macross: Do You Remember Love?: The scene where Hikaru watches the radar blips representing his squadron's missiles approaching the radar blips representing enemies while his heart is pounding loudly.
- Macross Frontier: When unmanned probes are first launched to examine the Vajra threat, all that is visible is a 3D display of their progress, followed by their symbols suddenly stopping and changing to say "LOST."
- Played for Laughs in Tenchi Muyo!. When Mihoshi first meets the group, her sensor alerts her that a vicious space pirate named Ryo-Ohki is in the area. She starts quaking with fear while everyone else just watches to see how long it takes her to figure out that Ryo-Ohki is actually the harmless Ridiculously Cute Critter sitting on Sasami's head.
- Wonder Woman Vol 1: During the Golden Age Paradise Island had a proximity alarm set up to alert the Amazons if anything was approaching the island from the sea. On one occasion despite the alarm being triggered their foes remained unseen while they scrambled to figure out what was coming since the villain had co-opted the tech that makes Diana's Space Plane invisible for a ship.
- Spoofed in the Parody Fic ALIEN!!!:
"Give me that bloody thing!" Kaneway grabbed the tracker off Tal, staring at its monitor. Thick pixilated blobs advanced menacingly down the screen. "What the... Tal you stupid moron, this is a video game!"
"That's it man!" cried Tal hysterically. "Game over, game over!"
- The Abyss: In the opening scene, a U.S. Navy submarine is tracking an unknown underwater object by sonar. The sonar blip is projected on a screen, showing the object maneuvering near the sub in the traditional (but incorrect) depiction of a sonar display.
- The Alien franchise:
- In Alien, while tracking the alien through the ventilation system.
- Twice in Aliens. The first time is after the dying woman is incinerated; as the xenomorphs begin to close on the Marines, Hudson notes the motion scanner going crazy, with the screen rapidly turning and the blips getting closer. The second time precedes the "They're crawling through the ducts!" scene. There's also the (deleted) scene where they watch the turret's ammo counters go down.
Hudson: Seven meters! Six!
Ripley: That can't be, that's inside the room!
Hudson: It's reading right, man, look! [...] Five meters! Four... what the hell?!
* Ripley checks her own scanner... and then looks up at the ceiling*
- Das Boot inverts this trope to great effect, as the sonar pings bouncing off the boat are being used to showcase how the Allied navy is hunting them.
- Close Encounters of the Third Kind has the air traffic control scene, where the aircraft (and possible UFOs) are represented not by blips as such, but by basic text and graphics on radar-like screens. This is Truth in Television, as that scene was filmed at Los Angeles ARTCC with actual controllers and radar displays. Modern ATC radar (especially at regional centers even in 1977) uses computer-generated data to display targets.
- Colossus: The Forbin Project does this with great tension as the supercomputers launch a nuclear exchange between the US and USSR, all the top heads can do is watch the radar and hope the machines will intercept the nukes.
- Crimson Tide has the scene where the U.S.S. Alabama has an encounter with a Russian Akula-class hunter-killer, leading to several minutes of playing cat-and-mouse and dodging torpedoes.
- In Deep Rising, the Argonautica's sonar operator counts down the distance between the cruise ship and the rapidly-oncoming whatever-it-is that's rushing towards it from below.
- Before its proper appearance, the monster in DeepStar Six makes itself known by appearing in the cast's radars, ramming something (usually with disastrous results) and then disappearing into the depths of the ocean.
- Done in Dr. Strangelove, when the missiles are approaching the nuclear bomber.
- Fail Safe: The story is largely told via humongous radar displays in the American war room and the generals' reactions to what they see on it. Aside from a few stock clips of fighter jets, which don't last 60 seconds combined, all of the action is set on the radar screen. It shares directors with 12 Angry Men.
- Forbidden Planet featured this during the third visit from the invisible monster. Radar showed something approaching, but no one can see it...
- Galaxy Quest: Played for Laughs
Guy: Red thingy moving toward the green thingy... I think we're the green thingy.
- The Giant Behemoth: Played with. In one scene, Dr. Sampson is in a helicopter over the Thames looking for the Paleosaurus, and sees it, but the radar operator at HQ claims there's nothing on the scope because for some reason the critter is invisible to radar detection (the movie never quite gets 'round to explaining why). Sampson insists he sees it, and this back and forth continues for a bit before the Behemoth puts the kibosh on it by unleashing its Death Ray upon Sampson's copter.
- This is done on the first Americanized Godzilla movie, where the submarine is tracking Godzilla approaching them at a high speed.
- Greyhound: As the movie is based around a WWII destroyer hunting U-boats, they rely on sonar and radar. Much of the time, if GREYHOUND can't see the target, neither can the audience, meaning the radar and sonar are the only ways we have of knowing where the target is.
- Harry Potter and the Prisoner of Azkaban uses a magical version of this with the Marauder's Map. Standing in a dark corridor, Harry looks at the map and sees an ink blot labeled "Peter Pettigrew" approaching him, unaware that Peter Pettrigrew is secretly scurrying about disguised as a rat.
- Hot Shots! plays this for laughs. Wash Out is tracking enemies closing in on U.S. fighter jets in enemy territory, when he sneezes on the radar display.
Wash Out: Oh my god, a dozen more of them! And a... blimp! A big, shiny blimp, and it's slowly moving south!
- In The Hunger Games: Mockingjay Part 1, during the bombing of District 13, President Coin and her staff watch the radar to know what's going on on the surface, while the bunker rocks from each missile hit.
- In Independence Day, as a clear Shout-Out to Super Dimension Fortress Macross, the assembled counterattack fighters and ground commanders watch as the little dot representing the President's missile flies all by itself towards the alien ship, wondering if the plan to disable the enemy's force fields worked. It impacts harmlessly against the shield. But then the Prez fires a second missile... everyone watches apprehensively... and it flies past the terminus line of the shield and explodes against the ship itself, showing it's now vulnerable to attack.
- The Loch Ness Horror involves sonar expert Spencer Dean using advanced underwater detection stuff to try and find Nessie.
- The first time the Bubble Ship is struck by lightning in Oblivion (2013), we get a glimpse of the Ship disappearing from the Tower's sensor display, much to the distress of Victoria.
- Predator 2: While the capture team is in the warehouse, the support team outside keeps track of the team and the Predator inside the warehouse using symbols on a screen. The suspense increases when the creature's movements indicate it can see the capture team and is about to attack them.
- Reign of Fire uses this to show the parachute squad's fight with the dragon, and it then creatively uses it to show you what happens when you don't deploy your parachute on time.
- Runaway: During the car chase scene, a large part of the tension is derived from a map screen showing Luther's smart bombs zoning in on the car.
- In The Thing from Another World, a Geiger counter is used to herald the title creature's approach.
- Used as Book Ends in Top Gun. In both cases, the MiG-28s are flying close enough together that the F-14s' radar reads them as half the number of planes that are actually in the formation.
- Parodied in Tremors 2: Aftershocks. The protagonists have rigged up seismic sensors to tell them when the subterranean graboids are approaching. While they're at their base of operations, the sensors start going off as if a huge one is headed right for them... until they look out the window and realize it's instead Burt and his oversized, overarmed military truck.
- Used extensively in Hollow Man, when the crew tries to locate invisible Caine via heat sensors.
- In Pacific Rim, the fisher boat's radar early on detects a rapidly approaching "island". Three miles off... one mile off... Kaiju!
- Honor Harrington: Due to the technology used in the setting, most navies have the capability to instantly detect ships exiting hyperspace, or using gravitic-based engines to move around. However, they are still largely limited to light-speed sensors and communications equipment to make any accurate identification of the ships in question. From time to time we see sensor operators trying to use whatever data they can glean from their gravitic sensors to make inferences about who or what just arrived in their star system. Oftentimes their guesses are wrong due to outdated intel or incorrect assumptions, and at least twice this has led to Friend or Foe? scenarios. The later development of faster-than-light communications (by a handful of factions) and various types of stealth further complicate things.
- The Lost Fleet uses the trope similarly, but unlike the above series the fleet tactics do not revolve around broadside Macross Missile Massacre tactics, so formations are complex and spread out enough that lightspeed lag matters when issuing orders.
- Used in several Tom Clancy novels, most notably Red Storm Rising. As usual of the Truth in Television variety.
- Death or Glory: Early in the book, Cain is in an escape shuttle. On two occasions (when he first jumps in, and when it arrives at Perlia) he refers to the large number of contacts on the auspex ... and the fact that the escape pod's systems aren't set up to identify whether those contacts are Imperial or Orkish.
- In the Star Wolf series by David Gerrold, due to the distances involved in a space battle no one ever sees their opponent. In fact, the first novel originally ends with the main character discovering that the enemy spacecraft they've been chasing the entire novel is just a sensor glitch (Gerrold later expanded the novel and had this just be an enemy ploy).
- In an audible version of the trope, the very first sentence of Isaac Asimov's science fiction novel The Stars, Like Dust is "The bedroom murmured to itself gently" (and the title of chapter 1 is "The Bedroom Murmured"). This "murmuring" turns out to be the sound of a radiation detector; the level of radiation it's detecting isn't enough to be harmful—yet—but what's making the detector "murmur" are the initial radiations from a "radiation bomb" that will soon reach the point of releasing a burst of radiation that will be deadly to, at the very least, the room's occupant.
The bedroom murmured to itself gently. It was almost below the limits of hearing—an irregular little sound, yet quite unmistakable, and quite deadly.
- Andromeda: Since engagements often take place over distances of light seconds, more often we see blips on the radar instead of actual ships.
- Battlestar Galactica (2003): "We've got multiple DRADIS contacts!" Battles between the Colonial Fleet and the Cylons were tracked on the radar-esque DRADIS system. A lot of dramatic turns involve signals popping up unexpectedly and at the worst moment. Season 2 episode "Final Cut" features a scene where a battle occurs offscreen and the audience watches the Galactica's crew reacting to the DRADIS screens and announcements from Dualla.
- Doctor Who:
- "Earthshock": The expedition base camp has a scanner that shows life signs moving around in the cave system the expedition is exploring. Over the course of the episode, we get dots suddenly disappearing (expedition members being killed), a dot that fades in and out (the thing that's killing them, which is alien enough to confuse the scanner), and dots suddenly appearing (the Doctor and friends arriving, just in time to be accused of the murders).
- The dragon hunt in "Dragonfire", a flagrant Alien homage.
- The Doctor's improvised motion-detector in "The Time of Angels". The blips get louder as the sound reflects off of objects in Amy's path; that she has to navigate a forest full of Weeping Angels, with her eyes closed makes it suspenseful. And then she trips, dropping the motion-detector.
- The 50th Anniversary mini-episode "The Last Battle" uses this with Arcadia's sky-trenches. The cameras and their accompanying sensors scan the skies... and then there's a blip. First comes one Dalek... and then millions of Daleks.
- Babylon 5: An early episode has Ivanova chasing down a lone raider and destroying it, only for a dozen other raiders to suddenly appear on her screen. We don't see how that turns out, just her back on the station being admonished for trashing her fighter.
- The Star Trek: The Next Generation episode "The Wounded" uses this to chilling effect. A rogue Starfleet ship is blowing up Cardassian ships as the Late to the Tragedy Enterprise crew watches on their tactical display. Every Cardassian logo going dark on the monitor is hundreds of lives lost and another step to a full-scale war...
- In The Last Ship episode "Friendly Fire", the Nathan James comes under attack from the Achilles at night, so the only way to track the incoming torpedoes is by sonar.
Sonar Officer Mason: Hydrophone effects, port bow. Torpedo inbound, bearing 1-9-0.
Sonar Officer Mason: Second torpedo incoming, same bearing first torpedo. 3,000 yards.
Sonar Officer Mason: Now three, now four torpedoes incoming. One minute to impact!
- Chernobyl uses this a lot due to the nature of radiation being impossible to actually see. Instead, you have Geiger counters increasingly beeping more often until it becomes a horrifying Hell Is That Noise.
- The Stinger of the final episode of Sea Monsters (part of the Walking with… franchise) shows the crew fast asleep as their radar begins beeping ominously. First one bogey approaches them, then another... and another... and soon, the ship is surrounded by a massive pod of Mosasaurs.
- Star Trek: Strange New Worlds has this in the episode "Memento Mori", where the heavily-damanged Enterprise is forced to hide from a Gorn ship in a brown dwarf. With the sensors of both ships not working, Spock comes up with an idea to use the navigation system's atmospheric sensors to track displacement, which is shown with a top-down view of the Enterprise and a blip representing the Gorn ship.
- In Good Omens (2019), the crew of a Japanese whaler are freaking out when the instruments keep showing the ocean floor seemingly rising up to meet them. The captain has no idea what to do think... and then giant tentacles appear to wrap themselves around the ship.
- Warhammer 40,000
- In the spin-off game Space Hulk has this as a game mechanic, being heavily inspired by the Alien series. Genestealers initially appear to the Space Marine player only as scanner "blips", each of which can conceal a variable number of the aliens. The number is only revealed when within sight of a Marine. Alien Assault is a computer game adaptation of Space Hulk's rules with an Aliens-esque setting, and also uses the scanner blips.
- In 40K proper, the Genestealer Cults deploy their armies behind sensor blips as a game mechanic, allowing them to play mind games with their opponents while they shuffle around their units. The blips are not revealed to be anything until they get in close to enemy units, allowing players to move strong units into position to attack without risking exposing them to heavy gunfire or sudden rushes from enemy units.
- Return to the Forbidden Planet: The cast wonder whether they have detected one or two things approaching their crashed spaceship. This leads to the line, "Two beeps, or not two beeps? That is the question."
- Any modern combat flight simulator when an enemy locks onto your fighter. Example. Averted in any tank simulator, since tanks mostly have no way of detecting incoming fire.
- The Alien vs. Predator games, naturally. The Marine's motion tracker has a number of quirks to it — it can pick up moving enemies, but also things like doors, loose wiring swaying in the wind, etc. It also works in regular pulses rather than real-time, so you're usually seeing where the xenomorphs were rather than where they currently are (i.e. about to pounce on you). And of course it can't pick up a cloaked Predator sitting motionless on a rafter.
- Alien Swarm: Intentionally, as one of its many Shout Outs to Aliens.
- Command & Conquer: Tiberian Sun had the Mobile Radar Array which, when deployed, could track enemies hidden by Fog of War, as well as Stealth and Subterranean units. The suspense part can even come into play with subterranean units, in that you can't tell whether what is about to pop up is a Flamethrower-tank or an APC loaded up with Cyborgs intent on murder — or Engineers about to steal your entire base.
- Command & Conquer: Red Alert 2 had an interesting example in the Psychic Sensor. It had a fixed range but could detect any unit that had the intent (orders) to go into that range.
- Command & Conquer: Red Alert 3: Inverted by submarine units, which are visible on the screen but don't show up on the minimap (or get shot except by dedicated anti-sub units) unless surfaced, meaning they can easily slip past a distracted player's defenses.
- DEFCON: The only hint of what might be really happening is the occasional sound of a woman crying.
- Uplink, a spiritual predecessor to DEFCON, had a program that would beep depending on how much time you'd have to hack into a target system before someone caught you in the act.
- Defender: The scanner was just a display of colored squares. But seeing humanoid abductions — and the high price of failing to prevent them — brings on the Sensor Suspense big time. The Ur-Example among video games.
- Fatal Frame: The player characters' paranormal sixth sense is represented by a filament that glows blue when a ghost is nearby... or orange if the ghost is hostile. The glow increases and decreases based on how close the ghost is and whether or not you're facing them.
- FreeSpace: "Multiple incoming jump signatures, hostile configuration!" Usually followed by "IFF confirmed, hostiles inbound!"
- Half-Life 2: Episode 2
- One scene has you defending a comatose Alyx against antlions with two other resistance members. The sensors are repurposed traffic lights that light up for the volume of ant lions incoming. The end of the scene has all of them light up as much as they can, forcing the player, the resistance, and a few other Vortiguants who came to help to fend them off.
- In the final battle for the silo, the car lights up as Striders attack from every point.
- Halo: Combat Evolved uses this in the level "343 Guilty Spark". As the Master Chief proceeds through a fetid swamp and into an abandoned underground Forerunner facility, he occasionally gets unknown motion tracker blips that disappear at the range of the sensor. Finally, after finding Pvt. Jenkin's mission recorder, a whole huge mass of unknown contacts begin to converge at the other side of a nearby door... Later in the same level, you meet up with a squad of surviving marines and fight the Flood in the swamp. If you get separated, you'll quickly find the last green blips disappearing from your sensor in the midst of the endless yellow.
- Homeworld: Playing the game entirely in sensor mode is like this.
- Metal Gear series: You will be looking at the radar minimap quite often, and you will most definitely notice when one of the blip's vision cones flips in your direction and turns yellow.
- Silent Hill: The radio starts playing static as dark things draw near. Silent Hill 4 instead uses this to indicate that the room is haunted.
- Starcraft II: The sensor tower, when first introduced in a gameplay demonstration, was used for this effect, particularly in one level where Raynor's Raiders are investigating a colony that's been infested by the Zerg. During the night, swarms of Zerg attack, showing up as an ! in the darkened areas of the map until they come into line of sight. However, the tower's Ao E is visible to enemy players.
- Sword of the Stars allows you to consult the sensor display in the tactical screen to keep track of BVR enemies, but you need upgrades to actually give orders from it. Somehow.
- X-COM: UFO Defense allows you to research and field motion detectors. They're a good way to avoid becoming Cannon Fodder when facing alien weapons, but since you don't know whether the blip is from alien or civilian (unless it's a very large blip, which would indicate a terror unit such as a cyberdisk or reaper) and on which floor, dealing with the results can be... interesting.
- In the MechCommander games, certain active enemy units are shown as blips when out of your vision range but within sensor range. Unless you have a skilled pilot and proper sensor hardware though, you have no way of knowing what that blip is; it could be a light scout vehicle or a fully-loaded assault 'Mech. The only exception is when a 'Mech starts up; the game does alert you to the boot-up in a rather melodramatic voice.
- Marathon, a 90s FPS from the developers of Halo: Combat Evolved, also had an Aliens-style motion detector. It only detected things that were moving; an enemy that remained still was invisible to it.
- In Mass Effect 3, the planet-scanning minigame gains shades of this, as you have to scan for special objectives in contested systems, but too many probes and the Reapers will see through your Stealth in Space.
- Several Shin Megami Tensei games, such as Shin Megami Tensei III: Nocturne and Shin Megami Tensei: Strange Journey, show a color-coded enemy sensor that does nothing but build anticipation: blue means everything's fine, and attacks will be rare. Yellow means there's a threat around. Red stands for "attack imminent." Sometimes the sensor will stay red for a while, especially in areas where one bad call or one bad turn at the RNG during a random battle can mean a game over, turning players into bundles of nerves. Strange Journey also has your HUD go off when a boss is in the area. "Warning: powerful demon detected." This actually warns you of several incoming ambushes, but it doesn't reduce the creep factor one bit...
- Etrian Odyssey presents an enemy sensor in the corner of the top screen, with identical color coding. An extra warning bar slides out if an F.O.E. happens to be nearby with lights indicating proximity, which is useful in case you weren't paying attention to your surroundings and didn't notice the giant orange fuzzball of doom bearing down on you.
- Total Annihilation laid the groundwork for a number of spiritual successors using various electronic warfare/intelligence systems; as maps could be quite large (even for the machines of the time) radar and sonar were essential, with detected units appearing as individual blips. Radar would pick up air and ground units (and buildings), whilst sonar picked up naval and submarine units. To complicate matters, you had no way of knowing what those units were without visual confirmation, and enemies could also build both jammers and spoofers that could either allow them to conceal units from your detectors, or generate lots of fake sensor returns to distract you from a flanking maneuver.
- Since Supreme Commander is one of the most large-scale RTS games out there (with maps going up to 81km squared in size), radar is essential to keep track of enemy units moving in the fog of war. You can't tell what kind of units they are until you get visuals on them, although experienced players can generally tell the difference between a swarm of land units, sea units, or different kinds of air units by their speed and formation; a patrol of high-tier interceptors will move a lot faster and smoothly across rough terrain than a gaggle of low-tier tanks, for example.
- In a similar vein, Ashes of the Singularity uses a heat-map-esque system for enemy movements and buildup in your radar range. A small reddish-orange blob isn't much to be concerned about, but when you see a giant yellowish mass slowly rolling toward your front line you might want to brace for impact.
- During The War Sequence from near the end of Zone of the Enders: The Second Runner you get a radar showing the battleground with your army of allies and oncoming swarms of enemies as different coloured dots. Not too tense, until you reach the final wave — when the entire top half of the rader is flooded by a ridiculous number of dots as a colossal horde of enemies starts sweeping down towards your poor outnumbered force. Oh, Crap! time.
- MechWarrior Living Legends has Enemy-Detecting Radar that can penetrate ground and buildings, but it requires line-of-sight to get a direct confirmation of the contact's model. That "Unknown enemy" contact around the corner might be a "Mr. Bubbles" Atlas BattleMech with all three of its rotary autocannons spun up. Electronic countermeasure suites allow vehicles to reduce their radar signature, which the advanced Angel ECM bubble expands to complete radar invisibility for allies in the bubble running passive sensors.
- Angels 2200: When Whiskey's motion detector goes off on the supposedly derelict Ellie Arroway.
- Exterminatus Now has one page where Virus is tracking a swarm of giant mutant spiders using a motion sensor as they come closer, closer... and then realizes he was holding it upside down and they're going in the opposite direction.
- Jonny Quest episode "The Robot Spy" starts with a scene at an Air Force base. Radar operators watch the approach of the title device on a radar screen before calling a Red Alert.
- The Simpsons: The Alien version is parodied in "Sweet Seymour Skinner's Baadasssss Song" when Bart brings Santa's Little Helper to school, and he gets loose inside the school air vents. Eventually, Willie is sent to catch him, with Principal Skinner monitoring on a highly advanced tracking system. For the air vents.
- One can only imagine what it must be like to be a military sonar operator or to have been a radar operator during World War II. Or worse, inverting things being on the receiving end of the former.
- Sonar units were intentionally left off some capital ships despite there being plenty of room and budget for them. Unlike lighter escort units that would be tangling with submarines anyway, the hydroacoustic kits would often have a demoralizing effect on the crew due to false contacts. However, it should be mentioned that half of this was so capital ships wouldn't try to investigate contacts directly rather than sending their escorts to do it.
- In modern air and naval warfare, this is effectively all there is as the odds of seeing an enemy have massively decreased with the advent of more modern missiles. With naval vessels, this has been true for several decades but for aircraft, it is only since around Desert Storm that this has become true.
- Modern parking sensors use beeps as indicators that you're reversing and reduce the interval between them the closer the vehicle's rear end gets to an obstacle until it flatlines at point-blank range. This system induces this trope on an incredibly mundane level.