For example, could I use a Intelligo Corpus spell with a range of personal, duration of instant, a target of boundary, and a Intelligo Corpus base level of 5 to know if someone is within my boundary and their location relative to me?
The Lower Limits of Magic imply that you need an Arcane Connection with things you do not sense to affect them but this limit is more flexible with Intelligo spells.
I would say: No. Not without Arcane connections to the targets.
That spell is similiar to The Inexorable Search, which requires an Arcane Connection.
I see the main problem in the fact, that you can't use Corpus with a target of boundary, Corpus needs to target a body (my interpretation)
Would I think could be done:
From Ars Magica Core Rulebook Page 113-114:
MAGICAL SENSES
Intellego spells can grant magical senses
to a person. These spells allow the recipient to
detect things that he could not normally sense,
and they have different targets, corresponding
to the kind of sense that the recipient gets. The
range of the spell is the range to the recipient.
Since you would get the senses yourself, Range Personal would be sufficient.
Then you don't get a "radar map" in your mind, intellego gives you the information through your normal five senses:
From Ars Magica Core Rulebook Page 114:
Taste: The information comes through the sense of taste. This target is equivalent to Individual.
Touch: The information comes through the sense of touch. This target is equivalent to Part.
Smell: The information comes through the sense of smell. This target is equivalent to Group.
Hearing: The information comes through the sense of hearing. This target is equivalent to Structure.
Vision: The information comes through the sense of sight. This target is equivalent to Boundary, but, unlike Boundary, it does not require Ritual magic.
That means , that you can't sense anything in the complete boundary, if you are not able to see, hear or smell anything in that boundary.
But you could sense any Corpus Target in Hearing or Sight distance (how far that is must be decided by the GM).
Hearing would have the advantage, you could sense targets behind you. But probably only a range of about 50-100 paces.
But, how does Sense the Feet that Tread the Earth function?
From Ars Magica Core Rulebook Page 154:
Sense the Feet that Tread the Earth (Level 30)
R: Touch, D: Conc, T: Part
You touch the earth and feel what is moving along the ground within a mile of where you stand. You can tell the direction, distance, weight, number, and manner of movement of moving things. For instance, you might sense "a single 50-stone creature slithering toward us, a hundred rods in that direction."
(Base 4, +1 Touch, +1 Conc, +1 Part, +3 size)
That is nearly what you want, only as a terram spell.
The Intellego Terram Guidelines states: Level 4: Learn one mundane property of an object. / See an object and its surroundings.
Here they got around the problem, because you sense a property of the ground which you touch, so no Arcane Connection needed. But you can't exactly know what is moving. Maybe with a corpus requisite you can only sense corpus targets.
I would say, the same is possible with Intellego Auram (you sense where there is a body which displaces the air, and since the air is around you, touch range is okay).
Intellego Imaginem should also work, but Target: Boundary would be a ritual.
But with corpus alone: I don't think it is possible.
No, unfortunately the spell design you've suggested does not work. There are a few issues:
1) You cannot target somebody unseen without an AC, or without affecting all targets within a contained area (room/structure/boundary), and the caster must still touch the room/structure, etc to cast. The range cannot be personal.
Using an enhanced perception spell with R: Personal also normally requires a link to a sense, such as T: Vision. So a R:Per and T: Boundary spell does not make sense.
An InCo base 5 R:Touch, T: Boundary will work, as it will give the caster an idea of where inside the boundary the person is. A second issue is that all Boundary spells have to be rituals which are expensive in vis.
2) The Base 5 you mention is for understanding a lot of detail about a body, and does not grant any special exception to the normal limits of magic with regard to targeting a person or thing which is not directly perceived, or that you have an Arc to. It is an extension of the base 4 guideline which only gives very general information.
e.g. Revealed Flaws of the Mortal Flesh directly demonstrates the base 5 guideline, and Physician's Eye demonstrates the base 4 (Ars p.130).
Here are some sample spells which might work:
Discern the Cardinal Path
Intellego Corpus 15, R: Arc, D: Mom, T: Ind
Caster gains knowledge of the current approximate distance and direction to the target with whom they have an arcane connection.
(base 3, +4 Arc)
You would need to Research a Breakthrough on the Lesser Limit of Arcane Connections for this to work. I don't have my books with me here, but I am pretty sure this is covered in Houses of Hermes: True Lineages under the Bonisagus section.
