Defining Land Mines using DF Traps Stats?

[Kallatari]

The title says what I'm trying to do. In particular, I'm looking more for the Detect, Disarm, and Save stats. For the rest, including effect, the stats are obvious and based on the explosives (which can be found in High-Tech).

I'm also trying to understand the logic behind the Detect and Save stats. Why are certain numbers or modifiers used as opposed to others?

Comments and suggestions appreciated.

Detect

So, I see to main methods here: tripwire, and pressure plate buried just beneath the surface.

Tripwire. I guess the starting point is the SM of the tripwire. Assuming a half-inch thick, the SM for thickness is -13, but it's an elongated shape, so +1 for -12. The tripwire is "in plain sight" giving a +10. So, assuming a 1/2" thick tripwire, this would be Perception -2. If we're going for really thin wire, this can probably result in up to another -5 penalty for the smaller SM. Therefore, we're talking Perception or Traps at -2 to -7 for most Tripwires. You could then apply any modifiers for Camouflage. Do these values seem reasonable?

Pressure Plate: I admit to being stumped here. The mine is technically not in line of sight, so it's by default impossible to see. No roll. However, I presume it might be possible to see a slight bump in the ground, recently moved earth, etc. So there should be a roll. I note in the new DF Traps, some have "pressure plates" in their description, and there appears to be the full range from no modifier to -10, but -4 seems to be the most common. So, it seems I would go with -4... but then it seems unintuitive that a Pressure Plate mine is easier to detect than one with a thin tripwire (which can range to -7). I'm definitely looking for suggestions here.


Disarm

To me, this is simple. Either Traps to remove the tripwire/pressure plate, or Explosives (EOD) to disarm the explosives. Failure on either triggers the explosives. Modifiers to EOD would be based on the complexity of the bomb; default mines (i.e., "store purchased") likely have no modifiers, while home-made explosives will have modifiers based on the maker's Explosive skill (and penalty he chose to make it with). I suppose Traps would be the same, but based on the Traps skill of the person setting it up.


Avoid

If you know where it is, you can simply go around it. Worse case, some sort of DX, possibly with modifiers, roll if you're in a narrow area and its difficult to avoid.


Save

And here again I'm stumped as to the logic behind the effect. I looked at DF Traps to try and judge how to stat this, but again it seems to vary quite a bit (understandably, as in the context of a DF game, the traps there are meant to present different challenges rather than always repeating the same thing).

I think the best effect is some sort of Sense roll to realize you hit the tripwire or stepped on the mine. If successful, you get to Dodge... which in this case means you dive for cover (at +3) to get that extra yard or two away so as to take less damage and minimize shrapnel. My question here is if allowing a Dodge is realistic for a mine? or "acceptable for a role-playing game realism"? Or, should this only be used in a cinematic game approach and in a realistic game the Save stat is simply "No"?

With mines and pressure plates, I know in many movies/TV shows, they step on the mine, here a click and pause... allowing an allyto defuse it. Is that an approach? So, Sense roll to here the click and then Do Nothing to not set it off? I assume there are also mines that would go off immediately, upon stepping on it (rather than waiting for the person to move off of it)? It makes for interesting dilemma as the PC must choose to whether he wants to wait and see or immediately dodge and take some sort of damage from the explosion. However, would the latter mines with immediately detonation even allow a Dodge roll?

Finally, is there a modifier to the Sense roll to notice you stepped on the mine or triggered a tripwire?


Other Stats

As mentioned, the rest are pretty easy. Damage is based on the mine itself It has 1 shot and cannot be rearmed after detonating, and you can certainly steal it.


So again, any advice or suggestions on how to quickly mark stats up for these traps is greatly appreciated.

[dcarson]

The tripwire is a straight line. Most things in nature are irregular so I'd give a +1 on Perception because ti contrasts with the surroundings.

[Bruno]

Re: pressure triggered, it really depends on how recently the mine was burried and in what sort of conditions.

Dungeon trap pressure plates are worked into the architecture - the whole room is flagstones, but this one flagstone isn't actually mortared in place because it's a pressure plate. Of course, other flagstones are going to be only partly mortared in place or completely loose because of crumbling mortar, so that's not a guarentee.

Other things to notice for that dungeon trap pressure plate are things like all the other flagstones being a bit more polished from people who know about the trap walking carefully around it, or being dirtier for similar reasons, depending on how close the area is to a source of new dirt. Possibly both! There's also the problem of obscuring gunge, like dungeon mold, stagnant nasty water, etc. but that's an additional penalty on top of whatever's going on.

Land mines planted outside lead to extra problems. The big one is plantlife.

In bare rocky/gravelly ground it's going to be sorta like flagstones, but more irregular. You could spot areas of loosely packed/disturbed gravel, if it was done recently. But it will repack over time.

If the land mines were planted in a grassy field this morning you could spot the cuts in turf, ground surface irregularities under the turf, and suchnot.

If they were planted in forest loam this morning, you can spot leaves that are damp on top compared to the rest of the litter being dry (indicating they've been disturbed), irregularities of the ground surface, dirt being loose vs packed, and general signs of disturbance in the area from the people setting the trap.

If they were planted ten years ago, you're pretty much hosed without things like a metal detector, or a trained mine-sniffing giant African pouched rat (... no I'm not joking, they're a thing and pretty effective).

[sir_pudding]

Originally Posted by Bruno

If they were planted ten years ago, you're pretty much hosed without things like a metal detector, or a trained mine-sniffing giant African pouched rat (... no I'm not joking, they're a thing and pretty effective).

Or clear it with explosives or earthmoving equipment.

[Kallatari]

Originally Posted by Bruno

Re: pressure triggered, it really depends on how recently the mine was burried and in what sort of conditions.

Alright, so for outside mines, let's say we start with a Vision (or Traps) -4 for a newly planted mine to notice fresh disturbances, etc., and that the penalty worsens over time until it reaches -10, and then at -11 at the next time interval, it effectively becomes undetectable by sight and you need special gear (or senses) to notice it. Is -4 a reasonable starting point?

Again, I'm going for an average. I realize it really depends on terrain, and how easily disturbances are noticed or hidden... but I'd lump that under a camouflage modifiers, giving bonus or penalties accordingly.

I know coming up with a "standard" modifier is nothing more than just a shot in the dark, but I like to have a "default" value, which I can then move up or down for easy or hard varieties.


Any thoughts on whether there should be a Save to dodge the blast once you trigger it?

[Kallatari]

Originally Posted by dcarson

The tripwire is a straight line. Most things in nature are irregular so I'd give a +1 on Perception because ti contrasts with the surroundings.

By the rules, is that a really a +1 to Perception, or a -1 to Camouflage the rope? Because by the rules, brightly colored clothes don't give a bonus to spot the person wearing them, but they do give a penalty to Camouflage that person.

Note, I also have issues with how this works and would personally agree with your interpretation, but fixing Camouflage is a likely a whole different subject matter.

[johndallman]

Originally Posted by Kallatari

So again, any advice or suggestions on how to quickly mark stats up for these traps is greatly appreciated.

The GURPS: WWII core rulebook has information on planting and finding mines, on pages 98-99 and 89. Given the new IP policy, I don't feel comfortable posting a quote, it would be several paragraphs.

[jason taylor]

Originally Posted by Bruno

Re: pressure triggered, it really depends on how recently the mine was burried and in what sort of conditions.

Dungeon trap pressure plates are worked into the architecture - the whole room is flagstones, but this one flagstone isn't actually mortared in place because it's a pressure plate. Of course, other flagstones are going to be only partly mortared in place or completely loose because of crumbling mortar, so that's not a guarentee.

Other things to notice for that dungeon trap pressure plate are things like all the other flagstones being a bit more polished from people who know about the trap walking carefully around it, or being dirtier for similar reasons, depending on how close the area is to a source of new dirt. Possibly both! There's also the problem of obscuring gunge, like dungeon mold, stagnant nasty water, etc. but that's an additional penalty on top of whatever's going on.

Land mines planted outside lead to extra problems. The big one is plantlife.

In bare rocky/gravelly ground it's going to be sorta like flagstones, but more irregular. You could spot areas of loosely packed/disturbed gravel, if it was done recently. But it will repack over time.

If the land mines were planted in a grassy field this morning you could spot the cuts in turf, ground surface irregularities under the turf, and suchnot.

If they were planted in forest loam this morning, you can spot leaves that are damp on top compared to the rest of the litter being dry (indicating they've been disturbed), irregularities of the ground surface, dirt being loose vs packed, and general signs of disturbance in the area from the people setting the trap.

If they were planted ten years ago, you're pretty much hosed without things like a metal detector, or a trained mine-sniffing giant African pouched rat (... no I'm not joking, they're a thing and pretty effective).

That is not necessarily a problem if it is part of an integrated fortification system(one of the favorite ways to use them) or if they are just dropped by the road "to whom it may concern"(that was a handy thing to do it; the Viet Cong used that as an economic use of it's less qualified personal while saving it's toughest guys for the toughest ops). In those two cases it does not matter that the enemy spots it, it only matters that it causes inconvenience.

In fact whether or not a mine can be found really only matters in an assasination. In war everyone knows that where one mine is another is likely to be so the mine has already done it's work whether or not it killed anyone.

[Bruno]

Originally Posted by jason taylor

In those two cases it does not matter that the enemy spots it, it only matters that it causes inconvenience.

True, but like dungeon traps, land mines stick around long after the people who lay them care particularly much about anything going on in their vicinity. And then you hit unintended targets.

EDIT: Regardless, that's neither here nor there for trap statistics - those do not care about the strategic use of land mines, just the individual problem of a land mine right now.

[jason taylor]

Originally Posted by Bruno

True, but like dungeon traps, land mines stick around long after the people who lay them care particularly much about anything going on in their vicinity. And then you hit unintended targets.

Quite so, but I assumed you were talking about limitations on the use of landmines and pointed out the limitations of the limitations. If we are talking about collateral after the war, obviously it is better that everyone know where they are.