Spotting caltrops?

[CountMRVHS]

What is the DC for a Perception check to notice caltrops?

*Is* there a Perception check allowed?

I've never sprung caltrops on PCs before - always thought of them as a tool for PCs to use against monsters, I guess. So I never rolled Perception checks for the NPCs to spot them; just did the attack rolls.

I think PCs would be annoyed if they didn't get the chance to even determine if there were caltrops in a given square, though. But I can't find any suggested DC in the caltrops section or the Perception section of the CRB.

Is there any DC out there that I just missed? If I had to guess, I might go with something like a DC 15 as the baseline, then adjust it from there with favorable/unfavorable modifiers. Caltrops must be pretty big in order to do what they do, but still it wouldn't be an automatic thing to spot.

[Chemlak]

House ruley as all hell, but you're right, there are no actual rules that cover this, but I would borrow from the Survival skill, as follows:

Perception : notice a visible creature: 0

Survival: Size of creature, fine : +8

Survival: Number of creatures (approximating 25 caltrops to a 2lb bag): -8

Modify by range and conditions, as per normal Perception rules.