Marksmanship is considered by many Rangers to be the bread-and-butter skill
that defines a Ranger.  Increasing Marksmanship increases the damage of a bow.
The actual damage equation is a bit complicated, but in general, 12 points in
Marksmanship against an AL of 60 will do 100% of the bow’s damage range. Also,
most bows have a minimum Marksmanship requirement.  If you wield a bow with
less Marksmanship than what is listed on the bow, then it does as much damage
as a bow of the same type dropped by a Level 5 enemy (the actual damage range
varies, just like those dropped by Level 5 enemies, and it is hidden).

Bow Damage Equations
====================
This is based on the excellent work done by SonOfRah, but it is subject to
change.  This information is accurate and tested as of July 2005.  For a more
detailed look at damage, check out SonOfRah’s guide at:
http://www.gwonline.net/page.php?p=157

The basic equation for Bow Damage is as follows:
Actual Damage = (Base Damage) x (Bow Bonuses) x (Skill vs. Armor Level)

The Base Damage is picked from the effective damage range of the bow.  For a
max damage bow, this range is between 15-28.  The Skill vs. Armor Level is
based on a complex equation, but a couple of general rules apply:
* Every point of Marksmanship offsets 5 points of Armor Level, up to an
  attribute rank equal to the character’s Level/2 (round down) + 2.  There are
  diminishing returns if your Marskmanship attribute rank is above Level/2
  (round down) + 2 (for Level 20, this is a value of 12). This “baseline” value
  is compared to the Armor Level of the target to determine the actual damage.
* Every point in Marksmanship above your Character’s Level/2 + 2 gives 2 points
  in addition to the baseline value below that threshold.  Thus at Level 20, a
  13 attribute Rank gives a baseline of 62.
* If the baseline is equal to the Armor Level of the target, then you do 100%
  of your damage.  If you have a higher baseline than the Armor Level of the
  target, then you do more damage.  If you have a lower Baseline than the Armor
  Level of the target, then you do less damage. 
* Every 40 Armor Level that the target has above your baseline halves the
  damage, and every 40 Armor Level that the target has below your baseline
  doubles the damage.

For example, since 4 points of attribute offsets 20 points of AL, you can
expect a Marksmanship of 4 (baseline of 20) to do half damage against an AL
of 60 (which is 40 points above the baseline).

An equation that models this behavior is as follows:
Damage = Base Damage * 2^{[(Baseline) - Armor Level]/40} * Bow Bonuses

Bow bonuses are multiplied with this along with the Armor Level calculation. If
you have multiple bonus percentages, then these percentages are multiplied
together.  I.E. A customized weapon gives a 20% bonus. When you combine it with
a 15% damage bonus, you multiply 120% and 115% to give a total of 138% enhanced
damage.  All damage is rounded to the nearest integer.

Hit Locations
————-
Guild Wars uses a Hit Location system.  This means that each piece of armor has
a chance of being struck individually, rather than an abstract armor level from
the pieces summed as a whole.  In general, these are the percentages:
* Chest is hit 37.5% of the time.
* Leggings is hit 25% of the time.
* Feet, Gloves, and Head are hit 12.5% of the time.

These percentages are augmented by positioning.  It is said that hitting the
head provides an increased or automatic chance for critical hits, but this has
not been confirmed.

Critical Hits
————-
Critical Hits always do maximum base damage of the bow.  They also give the
equivalent of -20 Armor Level reduction, increasing your damage by 41.42%.

The chance for a critical hit is not well-known, but the chance for getting a
critical hit is approximately 16% at attribute rating 12 (giving a chance of
about 1.25% per attribute point), with the chance for a critical hit doubling
for every 5 levels you are above the target, and the chance for a critical hit
being halved for ever 5 levels you are below the target. This is an approximate
equation that models the critical hit chance (but it may not be completely
accurate):
Chance = (1+[1.25*Attribute Rank])*2^([Character level - Target Level]/5)

Situational Damage
——————
It is not known if attacking from the flanks or from behind gives a measurable
damage bonus, although anecdotal reports seem to say that enemies who are
running away from you tend to take more damage.  Whether it is due to higher
chance of critical hits or from a damage bonus remains to be tested.  It was
thought that opponents did not get the benefit of a shield when attacked from
behind or the flanks, but this has been tested to be false as of 5/1/2006.

Attacking from an elevated position has a greater likelihood of hitting the
head.  Being above your target increases your range somewhat and grants a 15%
damage bonus.

Attacking from a lower position has a greater likelihood of hitting the legs
and feet.  No damage bonuses are known for this position.  Being lower than
your target reduces your range somewhat.

If your attack is a critical hit, the damage bonus from positioning is ignored.

Bonus Damage from Skills
————————
The bonus damage from skills is generally applied AFTER all armor and damage
percentage bonuses from the bow are calculated into the equation.  So if your
bow skill lists a bonus damage of +10, then +10 damage gets directly added
after calculations.  This means that armor generally has no effect on the bonus
damage done by Bow Attack skills.

The exception to this rule is Power Shot, for some reason, as this skill adds
to the Base Damage of the weapon rather than adding bonus damage after the
calculations (this fact is not confirmed, but it is in a few forum posts made
by SonOfRah).  This is important to know, because this means  that Power Shot
damage changes based on the armor level of the target.  A highly armored target
will take much less damage from a Power Shot, while a lightly armored target
will take much more damage from a Power Shot.

Damage Absorb
————-
Absorption provided from Runes of Absorption, certain item properties (Received
damage -2, for example), and Ascalon/Knight’s armor is directly subtracted from
the damage after all armor and damage percentage bonuses are applied, similar
to the bonus damage done by skills.  When up against non-Warriors, very few
things give a Damage Absorption bonus.  Damage Absorption is mostly in the
realm of primary Warriors, who have Knight’s/Ascalon Armor which gives a -3
Damage Absorb, Absorption runes (from -1 to -3 Damage Absorb), and magical
Damage Absorb mods on shields.  You will usually face between -4 to -9 Damage
Absorb on any particular warrior.  Damage Absorb used to apply to all damage
done to the target, even cutting back on damage that ignores armor. However,
the July 13, 2006 Update changed several types of Damage Absorb to only affect
physical damage.

Call of Protection is a Ranger skill that gives a lot of Damage Absorption to
your pet, allowing them to tank better.

Armor Penetration
—————–
Armor Penetration is a percentage adjustment of the Armor Level of the target.
For example, 10% Armor Penetration means that the base Armor Level of the
target is multiplied by 90% to determine the effective Armor Level.  Armor
Penetration comes in two varieties, Base AP and Bonus AP.  Base AP comes from
the Strength attribute, Penetrating Attack, Penetrating Blow, and certain Air
Magic spells, among other things.  Bonus AP comes from Judge’s Insight and the
Sundering weapon mod.  Only the highest value of base AP applies, but all
values of bonus AP stack on top of the Base AP.

The maximum armor penetration that a Ranger can have with a bow attack is 60%,
from a Sundering bowstring (+20% bonus AP) plus Judge’s Insight (+20% bonus AP)
while using a Penetrating Attack/Sundering Attack (20% base AP).

Damage over Time
—————-
The Damage over Time done by Conditions such as Poison and Bleeding are at a
rate of -2 Health per second per “pip” of degeneration, up to a maximum of 10
“pips”, or -20 Health per second.  This is not reduced by armor nor are there
any bonuses/penalties that augment this rate.  Conditions stack with each other
but not themselves.  The final Health Degeneration is determined by the sum of
all the Health Regeneration bonuses and the sum of all the Health Degeneration
Bonuses, so while you cannot go below 10 pips of Health Degen, you can apply
more health degen to offset gains from Healing Breeze, Mending, etc.

List of Health Degeneration Conditions
————————————–
* Bleeding        -3 pips or -6 Health per second
* Poison/Disease  -4 pips or -8 Health per second
* Burning         -7 pips or -14 Health per second

Some Marksmanship-linked skill highlights:

Barrage (Elite)
===============
Barrage is the spammable low-Energy Area Effect skill that Elementalists can
only dream about. At the quick Cooldown Time of 1 second and the low Energy
cost of 5 Energy (which can be brought even lower by Expertise), Barrage also
adds damage comparable to other Marksmanship skills.  This makes Barrage an
incredible weapon in the hands of a capable Marksmanship expert.

Barrage is an Elite skill and thus cannot be used with other Elites. Also,
Barrage is incompatible with preparations, as it removes all preparations when
it is used.  Keeping this in mind, Barrage works very well with bonus damage
enchantments from other classes, such as Judge’s Insight and the Elementalist
Conjure line.  It is a good way to soften up a group ganging up on a tank
(possibly your pet?), and often you can take down a whole group in just a
handful of Barrages in a row, and not break a sweat with your Energy bar. You
can also use Favorable Winds to increase your Barrage damage. Speaking of
which…

Favorable Winds
===============
Favorable Winds is an excellent “enchantment” in the Spirit line of Ranger
skills.  It lasts a long time, affects a large radius, and adds a significant
amount of damage and arrow speed.

Remember, this is a spirit, and thus also affects enemy arrows as well as all
of your allies’ arrows.  In a party of multiple rangers, sometimes it’s a good
idea to negotiate who will cast this spirit, so that only one person has to
carry the task of laying down this spirit.  Or multiple rangers can carry this
spirit and alternate laying down the spirit, speeding up the “recharge” time
for spirit coverage.  But if you are going up against enemy rangers, leave
this spirit at home.  Often, the monster groups will have many more archers
than you do, and will benefit far more from this spirit.

Penetrating Attack
==================
At first glance, this Bow Attack skill looks very similar to all of the other
Bow Attack skills.  It compares quite well to Power Shot, as it does a similar
damage profile.  However, it has a speedy cooldown of 3 seconds and 20% armor
penetration.  If you need a 10 Energy bow attack skill, this is the skill that
I would recommend, as it will probably deal the most damage out of all the 10
Energy Bow skills simply because it has 20% base armor penetration.  The fact
that its cooldown is among the fastest of the non-Elite bow skills is definitely
a plus.

With Factions, you also have access to Sundering Attack, which is a clone of
Penetrating Attack. Theoretically, you can carry both of these skills on your
bar and continually spam Armor Penetrating attacks for massive damage.

Pin Down/Crippling Shot (Elite)
===============================
Pin Down is the ubiquitous PvP snare skill.  A snare is a skill that slows your
enemy’s movement.  It has a rather long cooldown, and it is quite expensive at
15 Energy.  Nevertheless, it should be a staple in most PvP builds and certain
PvE missions (such as Aurora Glade).  Use Pin Down to cripple the Monk on the
opposing team, or to slow down Warriors so that you can run out of their Melee
range.

Crippling Shot (Elite) takes 15 Energy and a 1 second cooldown, and the Cripple
duration is 1-8 seconds. It cannot be blocked or evaded, either. Crippling Shot,
while typically having a shorter duration than an equivalent Pin Down, can be
spammed multiple times. Use Crippling Shot to disable several people with a
guaranteed snare (due to the “cannot be blocked or evaded” property). In short,
Crippling Shot is superior to Pin Down but it is still Elite, and thus takes up
your Elite slot.  On March 2, 2006, Crippling Shot was hit with the nerf bat and
significantly reworked.  It is still useful as a “spam crippling” attack, but
not nearly as powerful as it was before.

Read the Wind
=============
The only Bow Preparation in the Marksmanship line, Read the Wind provides many
of the same benefits of Favorable Winds.  The damage bonus from both skills
stack, but the arrow speed doesn’t appear to change much.  Being a preparation,
it does not stack with other preps.  However, it is a viable alternative to
Favorable Winds if one expects to face enemy archers in an area and wishes to
retain some sort of arrow speed bonus. Note that as of the 9/29/05 update, Read
the Wind got a duration boost to 24, bringing it on par with the other
“standard” Wilderness Survival-linked preps.

Factions Marksmanship-linked Skills
===================================

Some of the Marksmanship skills in Factions are close copies of existing skills
from the Prophecies campaign. For example, Sundering Attack matches very
closely to Penetrating Attack.  In effect, with both skills in your skillbar,
you can have two of that particular attack.

Broad Head Arrow (Elite)
————————
This is a skill that carries a lot of baggage: The arrow is slow, it has a long
15 second cooldown, it costs 25 Energy, and it is an Elite. It’s also possibly
the best Mage-killer in the game.  Unlike Concussion Shot, which requires you
to interrupt a spell to apply the “Dazed” condition, Broad Head Arrow adds the
Dazed condition, simply and easily.  If there happens to be a spell being cast
it also interrupts that spell, but that’s just icing on the cake.  It helps to
think of this skill as a “20 second spellcaster lockdown” rather than a standard
interrupt.

From a tactical standpoint, a clever Ranger can lockdown two opponents with this
and a standard bag of interrupts.  Just use Broad Head Arrow on one target,
preferably a target that’s already being attacked (perhaps by your pet?) and
use your standard interrupts on another opponent.  Alternatively, you can just
keep flipping between targets, shooting regular arrows to interrupt as needed
on the Dazed target and using standard interrupts on the other target.  This
works especially well against targets that use long-casting devastating spells
like Meteor Shower and resurrects.

Watch out for “block” and “evade”, particularly Distortion, Aegis, and Warding
Weapon.  Your arrow may be easily pre-empted by a wary spellcaster using arrow
dodging/blocking techniques, so it’s best used when catching a spellcaster off
guard. Also watch out for Condition removal.  In other words, this skill
probably won’t do very well in structured PvP with well-organized teams.

I found this skill to be invaluable in the Boreas Seabed mission.  You can lock
down the big bad bosses in this area (and you know which ones I’m talking about)
with a single skill.

If you need your Elite spot, and you are comfortable with your ability to
interrupt, you may want to bring Concussion Shot instead.  If you want a simple
way to shutdown spellcasters, though, this arrow will do the trick.

Updated on July 13, 2006: Cooldown was reduced from 20 to 15.

Focused Shot
————
It’s cheap, it has a fast cooldown, and does decent damage. The only penalty is
that it disables all of your other attack skills. Ouch.  Still, you can consider
bringing this skill as your primary attack skill, spamming it for repeated high
damage hits.  Good for skillbar economy, if your bar is full of spirits and
stances.

Updated on July 13, 2006: Now disables pet attack skills.

Marauder’s Shot
—————
Possibly one of the most damaging Bow Attack skills in the game, this skill
gives a huge bang for your 10 Energy buck, dealing more raw damage than even
Power Shot or Precision Shot.  The main disadvantage, however, is that it shuts
down all of your other non-Attack skills for 5 seconds.  This can be a problem
when you suddenly lose access to skills that you need, like Stances or Troll
Unguent.  The cooldown is a bit long at 6 seconds as well. Still, if you are
looking for a good sniping skill that deals great damage, you can use this.

Updated on July 13, 2006: No longer disables pet attack skills.

Melandru’s Shot (Elite)
———————–
Who says that Rangers have poor Energy reclamation? Melandru’s Shot (Elite)
gives a substantial amount of Energy and deals great damage to boot.  If you
are running an Energy-hungry build of some sort, and find yourself facing
Enchanted opponents all the time, perhaps this Elite will suit you. Unlike
other Energy Reclamation skills, this one is based on Marksmanship and the
Energy returned does not depend on the attribute.  It does take up your Elite
slot, however.

Needling Shot
————-
Another answer to the “Quick Shot” Ranger, Needling Shot does a small amount of
damage, but can rapidly fire if your target is below 50% Health.  Great to use
with preparations (which will probably be your main source of damage), and to
finish off a target.  If you bring along Quick Shot (Elite) as well, you can
really churn out the arrows by alternating Needling Shot and Quick Shot.
Because it has damage set by your Marksmanship skill, it can work well even
against heavily armored targets.

Seeking Arrows
————–
For the Called Shot lovers in all of us, this new preparation is short-lived,
but prevents your opponents from blocking or evading your attacks.  It is rather
expensive for a preparation at 15 Energy, but it is a great way to make sure
your interrupts and spike damage hits their mark.  Because it is a preparation,
though, your damage is likely to suffer, and it cannot be used with Barrage.

Nightfall Marksmanship-linked Skills
====================================

This section is a work in progress

Nightfall can possibly be called “revenge of the Bow Attacks” due to its large
“quiver” of new and diverse arrows to hail upon your opponents.

Burning Arrow (Elite)
———————
Extra damage AND burning? Where do I sign up? This attack combines a high
amount of bonus damage and the ever-popular and deadly Burning condition. With
Apply Poison or Barbed Arrows, you can smack a foe with the full -10 Degen in
a single shot!  For a quick takedown and high damage, it is difficult to
recommend another Elite.

Forked Arrow
————
It seems that while the developers are nerfing Dual Shot more and more, they
have a new “double arrow” attack up their sleeve in Nightfall.  This dual shot
does full damage with each arrow, unlike its original brother.  It costs 10
Energy, but the interesting thing is the fact that you only get two arrows if
you aren’t under the influence of a Hex or an Enchantment.  This presents a
sticky conditional situation, which makes this attack almost worthless in PvP
(how many times have you been hit with a Hex or an Enchantment).  It probably
can find some use in certain farming runs (low on Enchants and Hexes), but in
general, it would be difficult to use this attack unless you are an expert at
dropping Hexes/Enchants.