I think the layers need to start MUCH further out in order to give you time to actually react and manage..
Agreed.. That's where the '12 ga trip 'alarms' work the best... Give that first, 'sufficiently long-distance heads-up'. And, you can Easily 'DIY' with some BP and imagination (which I obviously can't detail, here..
..If you go 'silent' (IR / detector-eye)
First, then the tresspassers have time to Ingress,
further.... And you'd better make 200% sure that 'invisible layer' is
500% 'foolproof' (rain / bugs / heat / snow / ants (not kidding..) battery + solar-recharge B/U, etc, etc) because IF it fails, now they're that-much
further, in / you've got that-much Less time, etc..
..But, if the 'outermost layer' is audible from, say, ~1/4 mile out or more 1) you'll
Know (and, in-tandem with a 'protocol', ie: If someone in your group will be Out that far,
hunting w/ 12 ga, then Everyone Knows / is-informed, and there are 'comms to verify' if/when that Boom is 'ok' - or Not (ie:
'Kevin to Base, that discharge was NOT Me, all camp to DefCon One!!'.. etc..)
..then 2) the Trespasser now
Knows You Know, and just might be discouraged from going further (especially if they encounter
Our idea of a 'No Trespassing Sign' - see below..

:
..Now, I Do hear the 'other argument', also... That, if the intruder is alerted to the fact that they've been 'outed' (via the 12ga trip..) they could quickly 'sniper nest' (..IF they're so-armed / skilled.. I would
assume they
might-be..) and lie in wait for your Dogs / 'war party', etc that you'd then soon send out.. Even if you 'flank them', it could still end badly for you, so.. Why not 'let them enter' (but KNOW they did, via the 'stealth layer' (IR-trips, etc) and progress-in.. And then
You are the one that snipes Them...
..Agreed, that's an '
ideal scenario', but.. Something Else could just as easily 'tip them off', while they were progressing in (ie: Dogs hear the approach / start barking, etc - Now, they 'know you know', so Your 'stealth advantage' is blown..) But now, they're
closer IN... Not good...
..Of course, there needs to be 'overlap', and 'Zoning', so you know - pretty-much - what Quadrant of your property they first breached.. Then, via the Next layer (which I opin, is best to be One of the 'stealth-layers'..) will alert you -
Now that You're in DefCon One, and On your video-cams and/or drone-surveil, etc, approx which direction they Moved,
after the first-layer breach...
..For us, we've got it all mapped-out in an octagon / 'spider-web' type config.. Wiring is Done / hidden.. Trips / IR-lasers / eyes get added once we are Living On the BOL... We'll see how it goes, I guess..
..For Our BOL, at least, we've got a great situ, where there's pretty much only One 'in/out', that would be easy for anyone to approach-from.. The 'back-ways' are all solid-woods, and will be easy for us to cover with 'trip-surveillance'.. (and, much further Out, ie: roads off State roads (it's a good 2 miles from Any place a 'normal' vehicle can drive..)
..Point being, fairly easy to 'funnel' any 'casual walkers' / hikers / zommie gimme-dats, etc (who won't likely be prepared to make it up the Mountain / thru the woods, from the Other directions..) to the 'looks easy w/ a 4x4' entry points we
Want them to use... (where we can lay Other traps / mines, etc, also..)
..So, re: 'Trespassing Sign', heh, well.. Our plan - If people Get to the Entries of those 'entry-points' (before the 'trips'..) are 'movie-grade prop-cadavers', ie:
https://www.dappercadaver/
Note: ..I've purposely taken the '.com' Off, since the 'fake bodies' aren't 'dressed', and I don't want to 'get spanked' for posting a direct link...
Fair Warning: those pages might not be considered 'SFW' and/or yer little kids.. Or people who barf easily..

:
..So, we Got a couple of those (similar, not-Quite so good / expensive, etc) and several of the 'limbs' etc, and a few of those will be 'hung' at the Outer-quadrants of our property (again, Pre-trips..) with a prominent crude board-sign that simply says:
TRESPASSER 
:
..Also, because they'll be 'high up in Trees' (out of Bear / Coyote-reach..) they will have 'actual Gut / animal-blood' filings / splashes, etc, as I figure 'Crows pecking pieces off of them' will add to the 'sell'...

: We'll see how it goes.. Just figure that might send a 'stronger message' than a simple 'Trespassers will be Shot', etc.. No one Reads, anyway..
.02
jd