The rules were excluded from the 3.5e DMG if you have it look in the 3e DMG. A while back Kerrik posted a new spot rule system to handle exactly that. Since I can't find it and the great crash may have erased it I've posted his spot rules here.
Variant Spot System
The maximum distance one can spot a human-sized figure standing still, assuming flat terrain and clear conditions, is around 1,000 feet. Detail is impossible to make out you can't tell the creature's race, what it's wearing, or what it's doing, for the most part.
At 7-800 feet (3/4 max distance), the spotter can tell the creature's general size and shape, but exact identification is impossible unless the creature is very distinctive.
At 500 feet (half max distance), the spotter can determine the creature's general type (humanoid, giant, etc.) and may even be able to tell specific race, if it's distinctive; size, shape, and color are all evident, but individuals usually cannot be identified. Large banners can be idenfitied.
At 2-300 feet (1/4 max distance), individuals and smaller banners can be identified; broad actions (raising one's arms, drawing weapons, etc.) can be noted, but smaller ones (like pickpocketing) cannot.
At 25 feet or less, one can make out all but the smallest details. This range is reduced by 5 feet per size for a creature smaller than Medium, or increased by 5 feet per size for one larger.
The DC for spotting a human-sized figure at any range up to 100 feet, assuming clear line of sight and adequate illumination, is 5. At 100 feet, and each 100 feet beyond this, the DC increases by +2, to a maximum of 1000 ft. (DC 25). Each 100 feet is considered a sight increment like a range increment, but used for spotting purposes. The DC for spotting any creature at the maximum range for its size is 25.
Each size category larger than Medium increases the maximum range by 1 increment. Each size smaller decreases it by 1 (see Table 1).
If the target has or is a light source, treat its size as being one category larger for each size of the light source above Diminutive (candle). For example, a human carrying a torch (Tiny) would be treated as a Large creature; a campfire (Small) at night would be treated as a Large creature; a bonfire (Huge) would be treated as Titanic++ (-128 modifier, max range 138 increments, or 2.6 miles). Spell effects like light or daylight are treated as the normal light sources they mimic, where applicable (a light spell is equivalent to a torch, e.g.); a daylight or other spell that creates extremely bright light is treated as a Huge light source.
Small but extremely bright light sources (a daylight spell, e.g.) are treated as one additional size larger.
Figures around the light source can be seen out to half the maximum distance; a spotter can count (with a reasonable degree of accuracy) the number of creatures near the light, and can determine general activity, but attacks against them suffer a -4 penalty. At 1/4 max distance, figures around the light source can be attacked without penalty.
Table 1: Creature Size and Maximum Sight Ranges
Size Inc. Mod. Inc. Dist.
Fine +8 20
Diminutive +4 40
Tiny +2 60
Small +1 80
Medium +0 100
Large -1 110
Huge -2 120
Gargantuan -4 130
Colossal -8 140
Titanic -16 150
Titanic+ -32 160
Titanic++ -64 170
Titanic+++ -128 180
Increment Modifier: This is the number added to or subtracted from the creature's range modifier.
Increment Distance: The distance of a range increment for a creature of a given size.
Range Distance: The length of each range increment for a creature of a given size. For example, a Small creature can be spotted out to 9 increments of 80 feet each, or 720 feet.
Table 2: Visiblity Modifiers and Ranges
Condition Spot Mod.
Target is moving +2
Target is trying to gain
the spotter's attention1 +2
Target is raising a
dust/smoke cloud --2
Environmental conditions Range Inc.
Bright daylight 10
Mist, light rain 8
Dusk/twilight, light
fog/snow (<1/2 inch/hour) 8
Moonlit night (full moon) 6
Fog, moderate, heavy rain 4
Moonlit night (half moon
or less) 4
Moonless night, starlight 2
Heavy fog/blizzard/sandstorm --3
Terrain Inc. Distance
Plains/desert4 100
Hills 80
Marsh 60
Forest, light 40
Forest, medium 20
Forest, heavy/jungle 10
Mountains --5
Spot Modifier: This is the modifier to Spot checks, which applies at any range, regardless of how far away the spotter can see the target. These modifers can also be applied to ranged attacks, at the DM's option.
Range Increment: The number of range increments that can be applied. For instance, on a clear day, you can see out to the maximum range of 10 increments; at night, during a full moon, this is reduced to 6 increments.
Increment Distance: This is the distance of each range increment, according to the terrtain. For instance, a range increment on the plains is 100 feet, whereas one in light forest is only 40 feet. The maximum distance imposed by terrain always supercedes the maximum distance for a creature's size a Huge creature 500 feet away in dense jungle can't be seen, but it can still be heard.
1 Jumping up and down/waving its arms, signallling with a mirror or banner, etc.
2 A dust/smoke cloud is treated as being three size categories larger than the creature making it, so the Spot modifier and sight range increment are applied accordingly.
3 These conditions reduce all sight to 5 feet. Creatures and objects larger than Medium can be spotted slightly further away 5 additional feet per size above Medium but no details can be made out beyond the creature or object's general size.
4 Deserts with high dunes are treated as hilly terrain.
5 Since mountains cover the largest variety of terrain (from flat meadows to rugged hills and cliffs to winding canyons) it is best to apply the modifiers for another terrain type to the specific area.
Groups
Oftentimes, a character will spot a group of creatures on the move, or enemies will spot a party of adventurers. Either way, the same rule applies if the creatures are relatively close to each other (i.e., they are occupying bordering squares), they are treated as being a group, and are considered a larger creature for spotting purposes. In this case, use the size equivalency rules to determine the group's relative size (see below):
32 Fine = 16 Diminutive = 8 Tiny = 2 Small = 1 Medium = 1/2 Large = 1/4 Huge = 1/16 Gargantuan = 1/32 Colossal = 1/64 Titanic
Basically, two creatures of a given size equal one of the next larger size. For example: A flock of 50 birds (Tiny) are roughly equal to 1 Garganuan creature they could be spotted up to 14 increments (130 feet each) or 1,820 feet, away.
If a group of creature is raising a dust cloud, the same rule applies determine the group's size equivalent, then increase it by 3 categories for the dust cloud.
Elevated Positions and Spot Checks
A person standing in an elevated position (in a tree, on a tower/hilltop, flying, etc.) enjoys a much greater range of sight than someone on the ground due to the lack of ground cover and ground-level atmospheric distortions (heat waves, e.g.) interfering with line of sight. Each 10 feet above the ground grants the spotter a +1 circumstance bonus to Spot checks and ranged attacks, to a maximum of +10 to Spot and +5 to attack rolls. Each 100 feet above the ground lets you see one increment further, to a maximum of +5 increments. These bonuses do not apply in conditions that reduce sight to less than 10 feet fog clouds, sandstorms, etc.
By the same token, a creature in an elevated position (especially flying) is easier to see. The same modifiers apply to someone on the ground trying to see the target, but if the target has cover or concealment, these modifiers apply someone standing high in a tower looking out an arrow slit, for instance, can see very far, but is hard to be seen in turn.
Cover and Concealment
Even if someone is not attempting to hide, he could be standing in a position that makes it hard to see him there could be a large tree in the way, or the target is moving through heavy underbrush or is under the effects of a spell that makes him harder to see (blur, displacement, etc.). In this case, modifiers to the Spot DC should be applied. If the target is actively hiding, the rules for an opposed Spot check apply instead.
A general rule of thumb is that if the target has cover or concealment, the spotter suffers a penalty to see him partial concealment is -3, total concealment is -6, and cover can provide anywhere from -2 to -10. Note that these bonuses are cumulative someone standing in a dark room (concealment) on the other side of an arrow slit (near-total cover) would enjoy around a +14 bonus to avoid being spotted and also stack with the environmental conditions noted in Table 2, above. See the examples below for more details.
Examples
Here are a few examples of the Spot system in action.
Example 1: Durgan the fighter is riding across the plain in the middle of the day. The sky is clear and cloudless, providing great visibility (+0 modifier). About a half-mile down the road, another rider is coming toward him at a brisk trot, raising a dust cloud as he comes. The second rider is Large (horse-sized), but the dust cloud makes him three sizes larger (Colossal) for spotting purposes, which makes him seem 8 increments closer than he really is (or a -16 modifier to the DC). Since the rider is at max range for his size (around 2,500 feet), the DC is 25. Durgan can see the dust cloud with some effort, but he can't see what's making it until the rider draws closer (within 2,000 feet).
Example 2: Jasya the mage is standing atop her tower, admiring the sunset. Her hawk familiar is flying around nearby, looking for a snack, when it lets out a screech of alarm it has spotted a band of 8 orcs approaching the tower, about 200 yards away. The area around the tower is fairly clear except for low underbrush, but since Jasya is looking down, this has no effect on her line of sight. Since the orcs are moving as a group, they are treated as a a Huge creature for spotting purposes. Jasya is 50 feet up (+5 bonus), but it's twilight (-2). The orcs are 600 feet away, but since they're treated as a huge creature, this is only 3 increments (120 feet per increment, -2 increments), for a total of DC 14; with her bonuses, Jasya drops the DC to 11. She catches sight of the orcs easily and readies a fireball or two to deal with them.
For the orcs below, the DC to spot Jasya is a bit higher she's alone (Medium creature), which puts her at a full 6 range increments away (-12). Also, since the top of her tower has a low wall, she gains partial cover, which applies a -3 penalty to their Spot checks, for a total of DC 20 it's unlikely they'll see her until she starts casting spells.
Example 3: Kerrick the ranger is moving through a light forest on an overcast day (8 range increments of 40 feet each) when he hears something moving nearby (a brown bear, Medium size - +0). He stops and looks around, scanning the underbrush. Since it's a cloudy day, the maximum range Kerrick could see is 8 increments, or 320 feet. The bear is only 50 feet away, though DC 7. Kerrick can see it easily, despite the minor penalty.
