How precise is the detection granted by Detect Metal?

[wheatleymr]

Comparing Detect Metal:
"You attune yourself to magnetic fields, becoming aware of the presence or absence of metallic objects, veins, and deposits within the area."

to Detect Magic:
"You send out a pulse that registers the presence of magic. You receive no information beyond the presence or absence of magic."

Does Detect Metal allow you to detect e.g. "there are 3 collections of steel the size & shape of armour behind that door" or "there is silver and gold clustered underground over there"?
Or is it like the remastered Detect Magic, and it just reveals that "yes, there is hitherto unknown metal (steel, gold, etc.) within 30' of you".

[Ravingdork]

I would imagine it's the latter.

[NorrKnekten]

You detect the presence of metal, You can exclude metallic sources you are aware of, You do not learn the shape, size, amount of metallic objects or type of metal.

At rank 3 you can discern types. But if theres a pile of gold coins with a single gold painted brass coin you could not use the spell to discern which coin is the brass one.

[Finoan]

From what it says, it would be a binary 'detected' or 'not detected' for the entire emanation area.

How that is handled in a particular scenario may vary depending on how much time the GM really wants to spend on this scene.

For example:

NorrKnekten wrote:

But if theres a pile of gold coins with a single gold painted brass coin you could not use the spell to discern which coin is the brass one.

You could. You would have to cast the spell repeatedly while ignoring the other coins that are in the pile.

A linear search of grabbing one coin and casting the spell on it would mean n/2 spellcasts on average before finding the brass coin with a maximum of n-1 spellcasts.

A partition search of casting on half of the pile, then casting on half of the pile that is detecting as mixed type, and so on - means log2(n) spellcasts to find the brass coin.

Does the GM really want to spend that much on-screen time running that? Or just handwave it away and say that you can detect a brass coin in the pile and quickly figure out which one it is?

[NorrKnekten]

Log3(c+1) where c = coins yeah.
7 searches for a single bulk of coin.
11 for 100 bulk.

But that doesn't change that the spell cannot discern individual coins from eachother any more than a regular scale could. Nor could you know for sure whats causing that brass ping unless you physically rule out every other metallic object in the vicinity.

[Claxon]

Yeah, as written you couldn't determine which coin is gold in a pile, without examining each coin and ignoring the rest.

At that point it becomes like using a computer search algorithm.

You examine the whole pile and know at least one coin is brass.

You divide the pill in half, and examine one half while ignoring the other. Keep dividing in half until you find the fake(s).

[Ravingdork]

Just move half the coins out of the area. Then keep halving the pile of coins until you detect the odd one out.

We do it with low level detect magic in hoards all the time.

[Claxon]

Ravingdork wrote:

Just move half the coins out of the area. Then keep halving the pile of coins until you detect the odd one out.

We do it with low level detect magic in hoards all the time.

That works okay, but becomes more difficult if there are multiple items (10 gold coins in a pile of thousands). And it generally takes a lot of time.

[Ravingdork]

Claxon wrote:

Ravingdork wrote:

Just move half the coins out of the area. Then keep halving the pile of coins until you detect the odd one out.

We do it with low level detect magic in hoards all the time.

That works okay, but becomes more difficult if there are multiple items (10 gold coins in a pile of thousands). And it generally takes a lot of time.

Yep.