InCo Base 1 - Locate a person within a Circle or within Taste Range
InCo Base 2 - Locate a person within Touch | Eye* Range
InCo Base 3 - Locate a person within a Room or within Smell Range
InCo Base 4 - Locate a person within a Structure or within Hearing Range
InCo Base 5 - Locate a person within a Boundary** or within Vision Range
*Eye requires for the Target to be looking directly at you
**Ritual as usual
These guidelines do not allow you to see, they only allow you to locate where all people are within the target. You do not know who is there, you just know someone is there.
What does the community think?
There is already a guideline that covers locating a person ("Base 3 Locate a person"). See the core book, which also demonstrate a spell that uses that base (The Inexorable Search, p.131).
Note that a guideline does not specify the range, duration or target (including a sense). That is already covered by the spell building rules. The Base level applies to a R:Personal, D:momentary, T:Individual spell. Increasing each of the parameters adds a magnitude for each step and each parameter.
Edit: There are a few exceptions where the Base guideline specifes a range, but that is when it isn't the Range parameter, but rather a distance at which the target of the spell is projected. So the teleportation ReCo guidelines specify the maximum distance at which the target will be teleported. You still need to specify the Range at which you can cast the spell (Personal for yourself, Touch, etc.)
True but that guideline continues to restrict it to having an arcane connection to the person.
You saying that Base 3 should simply be used as such:
"Base 3 - Locate a person within a container or within a sensory range"
And we leave it to that?
That's essentially a result of the Limit of Arcane Connection (p. 80), which you couldn't bypass, even with a new guideline. You can detect human beings without knowing who they are using base 4, and you get a very general information for free as part of the detection spell. Merely detecting a human without getting information other than the number of detected individual can be done using the guideline from TMRE p. 93.
I am not in favour of guidelines that bypass Limit, even only lesser one. Especially when there is established spell and guidelines that allows to achieve the result by following existing rules.
I can say that canonically that guideline can be used without an AC, but that's been done at Touch, so it's exceedingly clear that the individual is specified well. As such, I don't see a problem using this guideline without an AC as long as you similarly don't violate the Limit of Arcane Connections. This generally means you're locating someone whose location you already know, as is the case with the canonical spell.
Meanwhile, considering canonically there is locating a person at Touch range using Base 3, I really wouldn't accept lowering that to Base 2 as suggested.
I can do this with no magic, using my eyes.
I am not entirely clear on what you want to achieve with these guidelines. Some possibilities violate the limit of AC, and thus are impossible (and the levels would be too low), but maybe you have something different in mind.
Seeing the location within the field of vision does not always mean that one can locate the person located there.
There are many examples where Intellego works without an arcane connection, in apparent contradiction to the Hermetic limit, and in fact, under this limit, the core rules state:
This is widely believed to be a flaw in Hermetic theory, as Intellego magic is much less tightly bound by this limit than other kinds
... but I am not going to speculate in OP's intention.
There seems to be some fuzziness about the meaning of "locate a person".
You seem to be reading it as "determine the position of a person relative to the caster".
However, in the corebook (The Inexorable Search) "locate a person" seems to mean "determine the position of a person on a map". So, for example, the following spell seems to a perfectly valid R:Per of the Inexorable Search:
Infallible Navigation (Intellego Corpus Level 4)
R:Per, D:Conc, T:Ind
Determines your location. You need a map to cast the spell; as long you maintain concentration, you can move your finger over the map at the rate of one hour per square foot of map; you can sense when your finger passes over your location as represented on the map (if you are not the area covered by the map, no sensations result). You can determine your position to within a thumb’s width on the map.
Base 3, +1 Conc
Exactly. On some meanings, this doesn't need magic. On others, it can't be done without an AC. I'm genuinely not sure what the OP wants to get, which makes it hard to judge the guidelines.
That's one example spell, but having a compass-like sense of where a person is with D: Conc seems like a perfectly fine spell. There are variations. Inexorable Search is just ideal for people who rely on maps for navigation.
They all, however, rely on having an Arcane Connection. Otherwise, you won't be able to target the person unless you can already locate them (which is basically what David Chart was talking about).
Note that the same guideline could be used, without an arcane connection, to determine the exact distance between the caster and a person that they see, so long as that person is within range (so R:Voice or R:Sight).
For clarity, the canonical guideline has been used for a person's location on a map, a person's celestial location (by Touch, so the caster probably knew where they were relatively), the distance and direction to a person relative to the caster, and a vaguely stated position of a person on a road. So there are a number of different canonically valid ways to use this guideline.
This is of course true if the goal is to locate a given person. However, somewhat similar to Miner's Keen Eye, it should be able to locate any person within sight, even to distant to be singled out by sight alone, without an arcane connection.
Actually, as I mentioned above, they don't all rely on an AC. There is a Touch one that does not, Convergence of Place (HP p.92).
Exactly. As long as you can properly target them, the Limit of Arcane Connections.
Isn't that the one that uses the Road target only accessible to those with Faerie Magic? I'd say that's a special case that overcome a limit of Hermetic magic.
No, CoP is T/M/I. It is used to determine the current celestial location of the target for calculating daily horoscopes.
"This spell is intended to be cast through an Intangible Tunnel." which usually presupposes you had an arcane connection.
Not really. Look at that chapter of HP. The tunnels in that section include The Evil Eye and The Master's Message, both of which open tunnels and neither of which uses an AC. If it weren't in the very section of the very book that intentionally uses non-AC intangible tunnels, I would agree with your statement. But considering the author is explicitly going into ways you can manage non-AC intangible tunnels right there, we really cannot assume the author thought intangible tunnels require AC's.
The spell is also in a section called Gathering Connections, which is explicitly concerned with you having a proper connection to the target.
Furthemore, the spell's purpose is to generate an horoscope as a Sympathetic Connection, which requires an AC.
So while not directly stated in the spell, I think there's indeed a built in assumption that you have an AC, which you likely used to open the tunnel in the first place and intend to explore together with the horoscope.
Still, extending the Level 3 guideline to work to locate people without the need for an AC should be no problem. And it would be in line with other Intellego guidelines to locate / get an image of a target, including that they are generally one magnitude lower than guidelines to get general information.
Of course, to locate a specific person you would still need an AC.
Barred that, the Level 4 guideline "Sense very general information about a body" should be enough to ascertain existence, and reasonably location, of a person. Still requiring an AC to locate or get information of a specific unsensed someone.