[Basic] Advantage of the Week: Scanning Sense

[johndallman]

Scanning Sense [Variable] is an exotic physical advantage. You can emit some kind of energy, such as radio or sound waves, detect it being reflected back to you and use this to sense objects in you surroundings. This is an “active” effect, which is detectable further away than you can sense anything. Unlike most senses, you can turn it off. This advantage appeared at GURPS 4e, as a generalisation of Radar Sense from GURPS Aliens for 3e.

What you can sense depends on the type of energy you use, but some things are constants:

• You can sense sizes and shapes, but not colours, fine details or surface markings, such as writing.
• The sense has a defined range, which you can modify with Increased Range or Reduced Range.
• Your signals are detectable at twice your sensing range, while the sense is turned on.
• You can use the sense in a 120° arc in front of you. You can buy this up: a 240° arc is +75%, a 360° arc is +125%.
• The sense is independent of ambient light, so you can ignore darkness penalties in combat.

The Basic Set defines several kinds of scanning sense, with their own prices, and new ones can be added. It does not specify details like pulsed vs continuous-wave radar, Doppler shift sensing and the like: those are left for players and GMs who want the extra detail to define for themselves.

• Radar [20] uses radio waves. You can only sense SM0 or larger dense objects, but your basic range is 2,000 yards. With a successful Sense roll, you gets a general idea of the size and direction of each object, and if it’s moving, but this is not good enough to aim attacks or form an image. You’re at ‑4 to sense anything that isn’t silhouetted against the sky, and can’t sense anything at all underwater. The Multi-Mode, +50%, enhancement for Radar gives you the ability to switch between Radar and Imaging Radar, although using an Alternative Ability would be cheaper. To use both simultaneously, buy them separately.
• Imaging Radar [20] uses radio waves at millimetre wavelengths, which behave rather differently. You can perceive small objects and shapes automatically, although you need a Sense roll to recognise a face, or similar complex shape. The sense passes through thin cloth or leaves, but more solid objects block it, and it doesn’t work under water. You get +3 to detect many kinds of concealed objects, and radar detectors are at -4 to detect your signals. Radar and Imaging Radar are the same thing for the Obscure advantage, per Powers.
• Ladar [20] uses one or more laser beams. This is quite like Imaging Radar, but with a slower scan and better resolution. You’re at ‑4 to spot things, but +4 to identify them. A specialised ladar detector is required to notice this sense, and rolls to use it are at ‑4. Obstacles are painful: you can’t see through anything solid unless it’s transparent to light, and dense smoke blocks you completely, as does magical darkness. Rain- or snow-fall cuts your range by 50-90% of normal, and being underwater reduces it by 99%.
• Para-Radar [40] works like Imaging Radar, but uses some kind of energy unknown to our current science, which works in any environment. Radar detectors cannot spot it, although equally advanced technology can. There’s a special Penetrating, +50%, enhancement for this form, which lets you see inside objects, as if you had Penetrating Vision 2.
• Sonar [20] uses ultrasonic sound. This has a range of 2,000 yards underwater, 20 yards in air at one atmosphere (multiply range by pressure in atmospheres) and does not work at all in vacuum. You can spot objects and determine general shapes automatically, but need a Sense roll to identify detailed shapes, such as faces. Anyone with Ultrahearing can detect your sonar; you can’t use it if you are deafened, and explosions or other loud sounds can disrupt it.

Any of these forms can have the Targeting, +20%, enhancement, which lets you “lock on” to a target and get its precise range and speed. This gives you +3 to hit with aimed attacks, as if you had a rangefinder. If you can only use Scanning Sense for targeting, and have to use some other means to detect potential targets, you have Targeting Only, ‑40%.

You can buy Acute Sense or Protected Sense for a Scanning Sense, with the GM’s permission. The Chameleon advantage can be bought for use against Scanning Sense, instead of normal vision. Having a Scanning Sense can be combined with Blindness for normal vision.

Sonar is the only Scanning Sense that’s found in real-world animals, and is quite common for aquatic creatures. Bio-Tech allows it to be bio-engineered into humans, while DF3 allows Bards to buy it, and psis to have Para-Radar. Magic offers Keen (Sense) for Scanning Senses, and a spell to grant sonar.

Powers adds two new forms:

• Active IR [20] uses an infrared laser beam, which you can turn off, leaving you with Infravision. It does not work underwater, but it can distinguish shapes as well as vision, and is only detectable via IR detectors and Infravision.
• T-Ray [25] uses very short wavelength radar, bordering on the infrared. It’s essentially a more precise version of Imaging Radar.

It also has three new enhancements, all worth +50%: Bio-Scan and Scanner are intended for rubber-science sensors, and let you use skills like Biology and Diagnosis at range, for Bio-Scan, and Chemistry and Physics with Scanner. No Intercept means your Scanning Sense is utterly undetectable.

Powers: Enhanced Senses adds detail: you are at ‑2 to detect things beyond base range, ‑4 at more than twice base range, and so on, ‑6 at four times base, and so on. Detecting a Scanning Sense at long range is at half that penalty. It also adds Megahertz Sonar, which is short-ranged, but quite detailed. Powers: The Weird adds a +50% enhancement that lets imaging Scanning Senses detect sound when it makes surfaces vibrate. Psionic Powers adds another form:

• Extra-Sensory Awareness [20] uses psionic energy pulses. Its range is only 20 yards, but it works in all environments, takes Para-Radar enhancements, and is as effective at detecting shapes as vision.

Supers adds one more:

• Field Sense [10] relies on electric fields that you generate, rather than pulses. This works like Radar, but with much shorter range, and also acts as a Detect for biological and mechanical electric fields. Your field is easy to detect.

I’ve never played or GM’d any characters with Scanning Sense. I’ve opposed lots of robots with it in the Reign of Steel campaign that spawned the Will to Live supplement, where we always assumed robots would detect us; the question was if they’d decide to do anything about us.

What have Scanning Senses done in your games?

[Michael Thayne]

You missed Ground-Penetrating Radar from Underground Adventures, which costs 20 points.

One question I have about Scanning Sense, sonar in particular: is there a good way, other than the aforementioned Ground-Penetrating Radar, to get a scanning sense that penetrates more than 1 foot underground? 1 foot is all you get from the Penetrating enhancement, by RAW, even though a couple books apply it to Sonar where I wouldn't expect the hard distance limits of comic-book "x-ray vision" to apply.

[whswhs]

Originally Posted by Michael Thayne

You missed Ground-Penetrating Radar from Underground Adventures, which costs 20 points.

One question I have about Scanning Sense, sonar in particular: is there a good way, other than the aforementioned Ground-Penetrating Radar, to get a scanning sense that penetrates more than 1 foot underground? 1 foot is all you get from the Penetrating enhancement, by RAW, even though a couple books apply it to Sonar where I wouldn't expect the hard distance limits of comic-book "x-ray vision" to apply.

Megahertz Sonar has a range of 200 yards in water or 2 yards in air. It might work for ground penetration. I haven't actually researched the geophysical use of sonar, though.

[Refplace]

Originally Posted by Michael Thayne

One question I have about Scanning Sense, sonar in particular: is there a good way, other than the aforementioned Ground-Penetrating Radar, to get a scanning sense that penetrates more than 1 foot underground? 1 foot is all you get from the Penetrating enhancement, by RAW, even though a couple books apply it to Sonar where I wouldn't expect the hard distance limits of comic-book "x-ray vision" to apply.

You can have multiple levels of Penetrating.

[Michael Thayne]

Originally Posted by Refplace

You can have multiple levels of Penetrating.

I suppose, though that doesn't seem to be strictly RAW. Also, it gets expensive fast—even if the base advantage only costs 20 points (like Sonar) that's still 10 points per foot of range or 30 points per yards.

[Refplace]

Originally Posted by Michael Thayne

I suppose, though that doesn't seem to be strictly RAW. Also, it gets expensive fast—even if the base advantage only costs 20 points (like Sonar) that's still 10 points per foot of range or 30 points per yards.

Pretty sure its in a writeup somewhere with two levels. As for cost that still makes it better than Penetrating Vision.

[Christopher R. Rice]

Originally Posted by Michael Thayne

I suppose, though that doesn't seem to be strictly RAW. Also, it gets expensive fast—even if the base advantage only costs 20 points (like Sonar) that's still 10 points per foot of range or 30 points per yards.

Originally Posted by Refplace

Pretty sure its in a writeup somewhere with two levels. As for cost that still makes it better than Penetrating Vision.

You're mixing it up from one of my books that isn't released yet...

[Refplace]

Originally Posted by Christopher R. Rice

You're mixing it up from one of my books that isn't released yet...

Doubt that, think I just always assumed it works that way.
I just checked Basic, Powers, Enhanced Senses, Weird, and Supers and did not find an example though.
The wording in Basic This functions exactly as Penetrating Vision 2
(p. 74). +50%.
Since Penetrating Vision can be purchased in multipole levels it seems reasonable that the enhancement can as well. But I can see a case for saying its not strictly RAW as its not specified either way.

[Christopher R. Rice]

Originally Posted by Refplace

Doubt that, think I just always assumed it works that way.
I just checked Basic, Powers, Enhanced Senses, Weird, and Supers and did not find an example though.
The wording in Basic This functions exactly as Penetrating Vision 2
(p. 74). +50%.
Since Penetrating Vision can be purchased in multipole levels it seems reasonable that the enhancement can as well. But I can see a case for saying its not strictly RAW as its not specified either way.

Yeah, you can't by RAW - not yet at least. GURPS Whatchamacallit addresses it though.