Artillery Spotting

Introduction:
This page studies the trigger rates & effectiveness of Artillery Spotting (弾着観測射撃), based on preliminary in-game testing. An optimal use of Artillery Spotting could considerably improve your fleet's daytime combat performances.

In brief, Artillery Spotting consists of two types of attack: Cut-In [CI] & Double Attack [DA]. When activated, the attacking ship receives a damage output (post-cap) & accuracy bonus. More detailed explanations could be found on the page Game Mechanics -> Artillery Spotting.

Typical Set Ups for Artillery Spotting:
Typical, basic set ups are listed below. Any additional equipment (eg. Sanshiki) will NOT affect their attack modes or trigger rates.

Double Attack

 * ...................2 x Main + Seaplane..........................................(basic setup)
 * ............2 x Main + Seaplane + Seaplane
 * ............2 x Main + Seaplane + Radar

''>> DA Damage: 120% (post cap) x 2. More powerful for ships with high shelling accuracy and against higher evasion, lighter armor units.''

Cut-In
''>> CI Damage: 110% / 120% / 130%. Works well for ships with high firepower while giving more chances for Artillery Spotting.''
 * .........................1 x Main + Sec + Seaplane.................................(basic setup)
 * .................1 x Main + Sec + Seaplane + Radar.....................(highest CI chance)
 * .................1 x Main + 1 x Sec + Seaplane + AP shell

>> Set up #2 triggers either secondary gun CI (110%) or radar CI (120%).

Hybrid (DA+CI)
''>> CI Damage: 130% / 150%. More CI expected than DA. Giving the highest base rate for triggering Artillery Spotting.''
 * ......................2 x Main + Sec + Seaplane
 * ......................2 x Main + AP shell + Seaplane

The Trigger Chance of Artillery Spotting: (Beta ver.)
Possible factors are listed below, followed by their estimated effects from experiments. These are best fit values from experiments, might be different from the actual ones, but they do give good estimates on the activation rates. To see how effects from each factor were evaluated, you may consult Mid-Term Report on the ASTRE Project.

The first 5 factors are assumed to have more solid basis: The following factors have negligible effects on the trigger rates: The following factors might have an effect on the trigger rates:
 * 1)  Being the flagship / 旗艦  (+15% for both rates)
 * 2)  Radar & type / 電探  (+30% CI chance, +10% DA chance, maximum)
 * 3)  Air control state (AS. AS+) / 制空権の状態  (-12% on both if only Air Superiority is achieved)
 * 4)  Fleet total LoS (FLoS) / 艦隊合計索敵値  (+8% DA rate, +10% CI rate, per 100 additional LoS)
 * 5) LoS stats on Seaplane /  水上機の索敵補正値  (minimal effects)
 * Type / number of caliber guns / 砲種 / 砲の数 (to be further evaluated)
 * 1) Fatigue / 疲労度  (No effect ?)
 * 2) Health state / HP (??)
 * 3) Level / レベル (Negligible effect ?)
 * 4) Formation / 陣形

Detailed Explanation:
1. Before we start, let's assume a standard situation, in which Fleet total LoS = 300, test ships are beyond minor damage(小破未満) and morale condition = 49. Fleet formation Line Ahead, and Air Supremacy (AS+) is achieved. Based on preliminary test results from 艦これ-チラ裏検証 & Homu Test, we may come up with the following hypothesis:

- BB(V) equipped with 2 x Main & 1 Seaplane has DA rate ~ 50%.

- CA(V) quipped with 2 x Main & 1 Seaplane has DA rate ~ 47% ?

- BB(V) & CA(V) equipped with 1 x Main + Secondary & Seaplane has CI rate ~ 50%

2. As total fleet LoS increases from 300 -> 400, the trigger rates increase slightly:

- DA rate + 8%, per 100 additional LoS.

- CI rate + 10%, per 100 additional LoS.

- Linear relation at any LoS level ??

3. If an additional seaplane is added onto the 4th slot:

- DA rate +5%

- CI rate +0%

- Actual effects are to be further tested.

4. If we use a radar on the 4th slot, and compare it with the standard situation:

- DA rate rises by 3% ~ 10%

- CI rate rises by ~30%.

- List of Radars with Estimated Artillery Spotting Rate Modifier
5. Different seaplane scouts vary slightly in the DA chance bonus.

- Type 0 Observation Plane & Prototype Seiran (+ 6 LoS) give the highest bonus. (+2%) ?

- Night Scout (+ 3 LoS) provides less bonus on DA chance (-2%) ?

- Different seaplanes have no effect on CI chance ??

- This part is currently neglected in DA/CI rate estimation.

- List of Seaplanes with Estimated DA Rate Modifier (Rough estimates)
6. For standard BB(V)s, aka non-Yamato class BBs, radars could be replaced by AP Shells for a cut-in setup (Main + Sec / AP / Seaplane), which gives a 20% trigger chance bonus on CI. However, you could also use AP shells (or Secondary) for a hybrid set up  (2 Main / AP (or Secondary) / seaplane). In the standard situation, the combined Artillery Spotting chance is about 70%.

- AP shell hybrid setup (with 41cm x 2): CI = ~38% & DA = ~32%. ?

- AP shell hybrid setup (with 46cm x 2): CI = ~43% & DA = ~27%. ?

- Secondary gun hybrid setup:              CI = ~50% & DA = ~20%. ?

- For hybrid setup, every 100 additional LoS will only increase CI chances by 5%.  ?

- Replacing Type 0 Recon by  Type 0 Observation Seaplane  will increase DA rate by 3%. ?

- These estimates are based on very limited test results, thus lower credibility.

- Brief Conclusion: Huge caliber guns and/or secondary gun on standard BB(V) would trade some DA for more CI chances.

7. If Air Superiority [AS] rather than Air Supremacy [AS+], then both rates fall significantly:

- Both CI & DA chance falls by at least 12%

- In the case of a hybrid setup, CI chance falls by 11% while DA rate -7%. ?

- If you're using the hybrid setup, it's more recommended to achieve Air Supremacy (AS+) for your fleet.

8. The flagship has a significantly higher chance (+15%) of triggering Artillery Spotting

- In the case of a hybrid setup, CI chance +7.5% while DA rate +7.5%. ?



Image source: 艦これ-チラ裏検証- .

Explanation: Blue = DA, Yellow = CI, Brown = Single attacks.
 * 1) TOP LEFT: Trigger rates for flagship (outer) & companion ship (inner) with hybrid setup
 * 2) TOP RIGHT: The plotting of artillery spotting rate versus fleet total LoS (flagship status &/or equipment bonus NOT excluded) 
 * 3) BOTTOM LEFT: Flagship & her companion ships with DA basic setup.
 * 4) BOTTOM RIGHT: Flagship & her companion ships with CI basic setup. 

Artillery Spotting Trigger Rate Estimate: (Beta ver.)
NOTE: As mentioned before, these calculation only serves as rough estimates on your ship's artillery spotting chances. More credible tests (#ATK > 170 for p > 70%, while #ATK > 256 for p < 60%, minimun) are required to come up with a better formula. Deviations from actual test results are supposed to be less than 5%, otherwise reworking on the formula itself could be considered. This does not include effects from HP status(小破・中破), and undetermined factors like formation & special ships / maps, etc. The estimates on which the true probability is closer to 50% will be less accurate.

Here's an example calculation in chart format, with sign convention:

Sample Calculation for DA:
1) Fuso Kai, AS+, FLoS = 300, equipped with 2 main, #32 radar & Zuiun. will have a:
 * DA chance of ...
 * 50%(BB Base) + 10%[Radar Modifier] + 0%(LoS Modifier) +1% = 61%

2) Prinz Eugen Kai, AS+, FLoS = 300, equipped with 2 main, FuMO32 & Ar196 will have a:
 * DA chance of ...
 * 47%(CA Base)+ 8%[Radar Modifier]+ 0%(LoS Modifier) +1% = 56%  

3) Chikuma Kai, AS+, FLoS = 400, equipped with 2 main, #22 radar & Type 0 Observation will have a:
 * DA chance of ...
 * 47%(CA Base)+ 3%[Radar Modifier]+ 8%(LoS Modifier) +2% = 60%

4) Haruna Kai, {flagship}, AS+, FLoS = 300, equipped with 2 main, #22 radar & Type 0 Recon will have a:
 * DA chance of ...
 * 50%(BB Base)+ 15%{Flagship Modifier} + 3%[Radar Modifier]+ 0%(LoS Modifier) = 68%

5) Mutsu Kai, {flagship}, AS, FLoS = 300, equipped with 2 main guns, #22 radar & Type 0 Recon will have a:
 * DA chance of ...
 * 50%(BB Base)+ 15%{Flagship Modifier} - 12%(Air Superiority) + 3%[Radar Modifier]+ 0%(LoS Modifier)= 56%

Sample Calculation for CI:
1) Fuso Kai, AS+, FLoS = 300, equipped with 1 main + 1 sec, #22 Surface radar & seaplane will have a:
 * CI chance of ...
 * 50%( BB Base)+ 26%[Radar Modifier]+ 0%(LoS Modifier) = 76%

2) Atago Kai, AS+, FLoS = 300, equipped with 1 main + 1 sec, FuMO25 radar & seaplane will have a:
 * CI chance of ...
 * 50%( CA Base)+ 26%[Radar Modifier]+ 0%(LoS Modifier) = 76%

3) Mutsu Kai, AS+, FLoS = 400, equipped with 1 main + sec, AP shell & seaplane will have a:
 * CI chance of ...
 * 50%( BB Base)+ 20%[AP Shell Modifier]+ 10%(LoS Modifier) = 80%

4) Kumano Kai, AS+, FLoS = 400, equipped with 1 main + 1sec, #32 Surface radar & seaplane will have a:
 * CI chance of ...
 * 50%( CA Base)+ 30%[Radar Modifier]+ 10%(LoS Modifier)= 90%

Sample Calculation for Hybrid Setup: (Rough estimate)
1) Mutsu Kai, AS+, FLoS = 400, Type 0 Recon, AP shell setup with 41cm x 2:
 * Total artillery spotting rate = 70%(BASE) + 5%(LoS Modifier) = 75%.
 * CI% = 38%(AP BASE) + 5%(LoS Modifier) = 43%
 * DA% = 32%(AP BASE) = 32%

2) Kongou Kai Ni, AS+, FLoS = 400, Type 0 Obsv., AP shell setup with 46cm x 2:
 * Total artillery spotting rate = 70%(BASE)+ 5%(LoS Modifier) + 3% = 78%
 * CI% = 43%(AP BASE, Overload) + 5%(LoS) = 48%
 * DA% = 27%(AP BASE, Overload) + 3%(Obsv.Seaplane) = 30%

3) Nagato Kai, AS, FLoS = 400, Type 0 Obsv., AP shell setup with 46cm x 2:
 * Total artillery spotting rate = 70%(BASE) - 18%(Air Superiority)+ 5%(LoS Modifier) + 3% = 60%
 * CI% = 43%(AP BASE, Overload) - 11%(Air Superiority)+ 5%(LoS) = 37%
 * DA% = 27%(AP BASE, Overload) - 7%(Air Superiority)+ 3%(Obsv.Seaplane) = 23%

DA:
- Lower activation rate compared to daytime CI.

- If each attack is counted separately, DA doesn't seem to increase shelling accuracy.

- More dependent on shelling accuracy if you wish to maximize your damage output (120% post-cap x 2)

- Using appropriate caliber gun set up (eg. 35.6cm x 2 on Fuso), ceteris paribus, BB(V) would have higher DA accuracy than CA.

- For CA(V) using DA setup + radar : - For BB(V) using DA setup + radar : - AP shells are accessible to BB(V), but provides a lower base DA chance. Once activated, the DA damage output could be devastating, but accuracy will not be guaranteed.
 * If head-On, T-disadvantage and/or low firepower, DA would usually be a double-scratch on the enemy with heavy armor (unless critical).
 * If high activation rate guaranteed (eg. flagship), DA is recommended when facing enemy with lower armor than Ru-Class Battleships.
 * In another word, if either attack could wreck the enemy, preferably using DA due to higher chance of hitting the target.

CI:
- Activate frequently during daytime battle (w/ radar), more reliable trigger-rate-wisely.

- It gives accuracy boost.

- If you're confident with your firepower, avoiding overkill on weak enemies and/or pursuing higher activation rate, CI + radar is usually a good choice. (eg. to prevent ships from stealing MVP)

- For CA(V) using CI setup + radar : - For CA(V) using secondary gun hybrid setup : - For BB(V) using AP shell :
 * Maximum damage is 120% post cap when radar CI is triggered.
 * Despite the highest activation rate, it provides a chance (~40%) to trigger secondary gun CI, which has only 110% damage modifier post-cap. This could be awkward when facing heavy armor enemies.
 * Since an additional secondary gun is added, while the CI damage modifier is 130% post-cap, this setup is more powerful when accuracy is guaranteed.
 * More CI expected than DA.
 * However, this setup does not provide vital accuracy bonus. Besides, the actual trigger rates need to be further tested.
 * 130% post-cap damage for CI setup + AP
 * 150% post-cap, for AP shell hybrid setup. More CI expected than DA.
 * Less volatile with respect to the changes in FLoS, and even more penalized when Air Supremacy is not achieved.
 * Preliminary study shows AP shell provide 10+ additional firepower against enemies with heavy armor. Therefore, this setup is quite recommended when dealing with Ru-Class Battleships and above.

General:
- Study on the effectiveness of BB(V) using AP hybrid setup, Comparative study on DA vs CI with sample enemies (by Nainodel).

- Although it is still uncertain that if using 46cm triple on non-Yamato class BB would affect their DA/CI accuracy, you may consult the following link as reference: Preliminary test results on the overweight penalty (source unknown)

Practical Use in Game & Suggestions

 * 1) Level up your ships & marry them. Ship levels affect their individual LoS stat, and a high FLoS would guarantee your ships to DA/CI frequently in battles. Also, if we assume a linear LoS growth, lv150 ships would have 50% more LoS than lv99 ships. It means if your central fleet is at lv99, they'd probably have FLoS ~400 (+10% DA/CI chance). When they're leveled up to lv150, you'll have FLoS ~600 (+30% DA/CI chance).
 * 2) Since fatigue doesn't seem to penalize the trigger rates while DA / CI boosts shelling accuracy, you could use it to counter fatigue. For example, leveling your ships at 3-2a with red faces. This method could drastically speed up your leveling, but less resource friendly (more buckets & repair cost).
 * 3) If ELoS (effective LoS) is prioritized, you wish to have more seaplane bombers, and/or you don't have good radars, equip an extra seaplane on your 4th slot is usually a good choice.
 * 4) For newer players, hybrid setup is recommended since your FLoS (fleet total LoS) is usually very low, which in turn will greatly penalize your ship's artillery spotting chances. Hybrid setup, however, has the highest base trigger chances while not so affected by FLoS. However, you should always get AS+（制空権確保） and maximize your ship's firepower through modernization. Please be aware that using 2 x Main + 1 x Sec would shift your DA into CI in night battles, which is very dependent on luck stat & placement (flagship)..

Uncertainty

 * In K-Test, if we compare no.7.8.9 versus no.15, we could see as FLoS increased from ~250 to 356, DA chance from Takao Class CAs didn't change at all. According to the FLoS calibration method, this gives an error of 8.5%, which is way above our tolerance. Is that a coincidence or something?