Blindness and Dark Vision- please help me clear it up

[Bruno]

Originally Posted by Flyndaran

Sounds kind of like impossibly high definition sonar only without a detectable emitted sound.

Frequencies approaching 540–580 THz, even :) Medical imaging ultrasound is 1–20 MHz, so there's a big gap.

Without a detectable emitted sound and with the same sort of nigh-indefinite range that GURPS vision gets, rather than the flat cut-off sonar and other Scanning Senses get. That said, this is a character who's vision would be rapidly choked off by mist, rain, dust, etc - remembering that they don't experience transparency or translucency - it's all opaque.

In the D&D context this is usually hand-waved by mumble mumble ambient magical energy mumble. I've wanted it as the foundation for a character who perceives their environment through retrocognition/psychometry; they can "see" surfaces based on the contamination of psychic traces attached to them, and people/animals because they're little balls of emotion. Plants, on the other hand, not so visible (*bonk* Who left this tree here?).
Obviously they get Psychometry also in order to look at those traces more closely, but I need something separate to get them to navigate their environment.

[vicky_molokh]

What sharp cutoff? Scanning Senses suffer a -2 per doubling past the rated range.

[Bruno]

Originally Posted by vicky_molokh

What sharp cutoff? Scanning Senses suffer a -2 per doubling past the rated range.

I don't see anything like that in the description of the advantage.

EDIT: To show my work, I've only checked Basic Set and Powers, but Powers has nothing at all to say about the issue and Basic Set says only

Originally Posted by Basic Set Page 81

Your sense is “active.” Anyone who can sense the signal you emit can detect you, out to twice your own range. Unlike other sensory advantages, however, you can turn this ability off; see Turning Advantages Off and On (p. 34).
Below are several varieties of Scanning Sense. Each is a separate advantage, with its own special rules. Where these rules contradict the general ones given above, follow the special rules. Each sense also has a base range. To adjust this, take Increased Range (p. 106) or Reduced Range (p. 115).

Particularly the rules for signal detection and LPI seem to also refer to your base range as a hard cut-off.

[Kelly Pedersen]

Originally Posted by Bruno

I don't see anything like that in the description of the advantage.

Powers: Enhanced Senses clarifies this: "Scanning senses have a base range; each doubling of distance beyond this range imposes ‑2." (p. 6). This is also how the active sensors in Ultra-Tech work.

Originally Posted by Bruno

Particularly the rules for signal detection and LPI seem to also refer to your base range as a hard cut-off.

I would assume that the same -2 applies to detection for each multiple of the increased range. So, Radar could be detected at no penalty out to 4000 yards, at -2 between 4000 and 8000, at -4 between 8000 and 16000, and so forth, while Radar with Low Probability Intercept would have a "base detection range" of 1500 yards.

[vicky_molokh]

Originally Posted by Kelly Pedersen

Powers: Enhanced Senses clarifies this: "Scanning senses have a base range; each doubling of distance beyond this range imposes ‑2." (p. 6). This is also how the active sensors in Ultra-Tech work.

It's also how SSes work in Basic Set: Campaigns.

[Bruno]

Well, I'm pleased to hear this. My mutant with Sonar in Mlangsdorf's ATE game will be extra pleased.

[David Johnston2]

Originally Posted by Bruno

I don't see anything like that in the description of the advantage.

It's a question of what "base range" means. It doesn't mean the same thing as "range".

[scc]

I'm pretty sure this has come up before and if I'm remembering things correctly Dark Vision isn't actually vision based, no light is involved.

[Anthony]

Originally Posted by David Johnston2

It's a question of what "base range" means. It doesn't mean the same thing as "range".

In fact, it does mean the same thing as range. The way scanning senses works is needlessly complex (-2 per doubling is close enough to the range/speed chart as to make no useful difference)

[David Johnston2]

Originally Posted by Anthony

In fact, it does mean the same thing as range. The way scanning senses works is needlessly complex (-2 per doubling is close enough to the range/speed chart as to make no useful difference)

No, it means the "range at which there is no modifier to the die roll".