# Solver options

Every solver option in a few lines: what it is, what each of the four models uses, when it matters and what it interacts with.

## Index

This page is generated from each option page and from the solver.
It lists every solver option in a few lines. Read the block for the option you care about, and open its page only when the block is not enough.
Each block gives: the setting and its key, a summary, the choice each of the four models makes, when it matters, and what it interacts with.
Model choices are shown as the labels the app uses.

**Drag table** (`dragTable`) — [page](options/dragTable.md)
Which published drag curve the bullet flies on, and whether the Standard model's small correction near the speed of sound is applied; also how the drag deceleration is built from it.
Models: Standard: G7, adjusted (Standard) · Physics: Plain published table · Classic: Plain published table · Spin: Plain published table
Matters when: G7 bullets slowing through about Mach 1.05 and below (past roughly 2,400 yd for a 350 gr bullet at 3,000 fps in the 2-mile scenario's air); nothing on G1 bullets or on shots that stay above that speed
Depends on: nothing

**Coriolis** (`coriolis`) — [page](options/coriolis.md)
How the Earth's rotation moves the bullet: a drift formula plus a change in gravity, the full acceleration at every step, or nothing.
Models: Standard: Simple formula (Standard) · Physics: Integrated along the flight · Classic: Off (Classic has no Coriolis) · Spin: Integrated along the flight
Matters when: long flights; the sideways part grows with time of flight and latitude, the vertical part with muzzle velocity, range and how far east or west you shoot
Depends on: `flight`

**Elevation angle** (`angle`) — [page](options/angle.md)
How the drop at the target becomes an elevation in mil, and, for the Classic choice, how the sight height is counted on a slope.
Models: Standard: Drop ÷ range (Standard) · Physics: True angle (arctangent) · Classic: Classic (sight height ÷ cos slope) · Spin: True angle (arctangent)
Matters when: the true-angle value matters only at very large come-ups (a few hundredths of a mil at 50 mil); the Classic value matters on steep slopes at short range (about 0.1 mil at 100 yd on 30°) and fades with range
Depends on: `flight`

**Wind in drag** (`windDrag`) — [page](options/windDrag.md)
Whether drag is worked out from the bullet's speed over the ground or from its speed through the moving air.
Models: Standard: Ground speed (Standard) · Physics: Speed through the air · Classic: Speed through the air · Spin: Speed through the air
Matters when: head and tail winds, and long shots where the bullet is near the speed of sound; a pure crosswind changes almost nothing
Depends on: nothing

**Air along the path** (`lapse`) — [page](options/lapse.md)
How air density and the speed of sound change with height during the flight.
Models: Standard: Line of sight (Standard) · Physics: Bullet’s real height · Classic: Classic (line of sight, from your altitude) · Spin: Bullet’s real height
Matters when: steep shots and very long range; nothing on a level shot inside about a mile; the Classic values also depend on the site's altitude
Depends on: `tempClamp`, `flight`

**Speed of sound** (`soundSpeed`) — [page](options/soundSpeed.md)
Whether the speed of sound at the rifle comes from temperature alone or also from humidity.
Models: Standard: Dry air (Standard) · Physics: Humid air · Classic: Dry air (Standard) · Spin: Humid air
Matters when: humid air, especially hot; any shot that passes through the transonic range, where drag changes fastest with speed
Depends on: nothing

**Gravity** (`gravity`) — [page](options/gravity.md)
Whether gravity is the fixed standard value or the value for the shot's latitude.
Models: Standard: 9.80665 m/s² (Standard) · Physics: By latitude (WGS-84) · Classic: 9.80665 m/s² (Standard) · Spin: By latitude (WGS-84)
Matters when: every shot, by a small steady amount that grows with drop; most visible at very long range
Depends on: nothing

**Air density (humidity)** (`airDensity`) — [page](options/airDensity.md)
Which density of humid air the drag uses at the rifle: a simple humidity correction, or the exact mix of dry air and water vapor.
Models: Standard: Simple humidity correction (Standard) · Physics: Exact humid air · Classic: Exact humid air · Spin: Exact humid air
Matters when: hot, humid, thin air (high and hot) at long range; nothing in dry air or near sea-level pressure, and only a small amount in cool mountain air
Depends on: nothing

**Water vapor in hot air** (`vapour`) — [page](options/vapour.md)
How much water vapour the air holds: the usual saturation formula, or the classic reference's smaller amount above 80 °F.
Models: Standard: Usual formula (Standard) · Physics: Usual formula (Standard) · Classic: Classic (less vapor above 80 °F) · Spin: Usual formula (Standard)
Matters when: hot, humid air, well above 80 °F; nothing at or below 80 °F and nothing in dry air
Depends on: nothing

**Temperature on slopes** (`tempClamp`) — [page](options/tempClamp.md)
On cold or hot days, how the air cools or warms along a slope for the three Classic air choices, easing back toward a normal day on one side.
Models: Standard: Off (Standard) · Physics: Off (Standard) · Classic: Classic (cold or hot days ease toward normal) · Spin: Off (Standard)
Matters when: steep shots on days much colder or hotter than normal for your pressure, when "Air along the path" is one of the three Classic choices; nothing on a level shot at the line of sight's height
Depends on: `lapse`

**Spin drift** (`spinDrift`) — [page](options/spinDrift.md)
How far a spinning bullet drifts sideways in calm air, either from a published formula in time of flight and stability, or as a fixed fraction of the come-up.
Models: Standard: Litz formula (Standard) · Physics: Litz formula (Standard) · Classic: Classic (fraction of come-up) · Spin: Litz formula (Standard)
Matters when: every long shot (the drift is a few tenths of a mil at 1,000 yd and over a mil at 2 miles); the two values differ most at long range and on slopes, and the choice is moot under the Spin model, which integrates the drift
Depends on: `dynamics`

**Aerodynamic jump** (`aeroJump`) — [page](options/aeroJump.md)
The small up or down shift a crosswind at the muzzle gives a spinning bullet: a published formula that depends on the bullet, or a fixed amount per mph.
Models: Standard: Litz formula (Standard) · Physics: Litz formula (Standard) · Classic: Classic (constant per mph) · Spin: Litz formula (Standard)
Matters when: any shot with a crosswind at the muzzle; it is the same at every range, so it is largest compared with a short come-up, and it is zero for a head or tail wind
Depends on: `dynamics`

**Bullet dynamics** (`dynamics`) — [page](options/dynamics.md)
Whether the bullet is a point with drag and gravity plus formulas for spin drift and jump, or a spinning body whose spin, yaw, lift and Magnus force are flown.
Models: Standard: Point mass (default) · Physics: Point mass (default) · Classic: Point mass (default) · Spin: Spin (spin and yaw)
Matters when: long flights, where spin drift and the small lift and Magnus forces on the bullet's yaw add up; crosswind at the muzzle (the jump)
Depends on: `magnus`, `estimatorRules`, `yawRepose`, `subsonicLift`, `aeroJumpSpin`

**Earth curvature** (`curvature`) — [page](options/curvature.md)
Whether the Earth's curvature is taken to have lowered a distant target below the horizontal line you entered as the slope.
All four models: Off
Matters when: a slope angle that came from map heights rather than from an angle meter, on long shots; nothing when the angle was measured
Depends on: nothing

**Flight to each range** (`flight`) — [page](options/flight.md)
Whether each range's come-up is read off one flight with your zero, or off a fresh flight dialed for that range.
All four models: From the zeroed path (default)
Matters when: long shots with a lot of come-up (the two agree closely inside about 1,500 yd) and steep shots; also the arrival velocity and time of flight, which differ even where the come-up barely does
Depends on: nothing

**Magnus force** (`magnus`) — [page](options/magnus.md)
How strong the small upward push from the bullet's spin is taken to be, and how it changes with speed, in the Spin model.
All four models: Automatic (default)
Matters when: long flights under the Spin model, where the push grows with time of flight; nothing under any other model
Depends on: `dynamics`

**Estimated coefficients** (`estimatorRules`) — [page](options/estimatorRules.md)
Which typical values the Spin model starts from when it has to estimate a bullet's aerodynamic coefficients from its weight, size, length and construction.
All four models: Standard coefficients (current)
Matters when: the Spin model on a bullet with no attached coefficient set, which is every bullet nobody has measured; it moves spin drift most, and come-up a little at long range
Depends on: `dynamics`, `yawRepose`

**Yaw of repose** (`yawRepose`) — [page](options/yawRepose.md)
Whether the small angle the spinning bullet flies at to its path is worked out from gravity (and the Earth's rotation) alone, or from the bullet's own lift and Magnus force as well.
All four models: Automatic (default)
Matters when: Spin model only; long flights, where the yaw has grown and the extra upward push of the full form adds up to about a hundredth of a mil of come-up at 2,000 yd, a few hundredths at two miles
Depends on: `dynamics`, `estimatorRules`

**Lift below the speed of sound** (`subsonicLift`) — [page](options/subsonicLift.md)
Whether the bullet's lift, in the Spin model, is cut to about two thirds of its Mach-2 value once the bullet is below the speed of sound.
All four models: Standard
Matters when: long shots on which the bullet is near or below the speed of sound for a long stretch (on the 2-mile scenario's bullet the effect is negligible until about 2,500 yd), where spin drift and the nose-up push depend on the lift
Depends on: `dynamics`, `estimatorRules`

**Crosswind jump (Spin model)** (`aeroJumpSpin`) — [page](options/aeroJumpSpin.md)
How the Spin model works out the small up or down kick a crosswind at the muzzle gives the bullet: from its spin, shape and lift by the classical theory, by the app's earlier form of it, or from a formula of its stability and length.
All four models: Classical theory (Standard)
Matters when: a crosswind at the muzzle with the Spin model; the values can differ by a third or more
Depends on: `dynamics`

**Zero offset** (`zeroOffset`) — [page](options/zeroOffset.md)
Whether the profile's stored zero height and zero offset shift every come-up and windage, or the rifle is taken as zeroed exactly on the aim point.
All four models: Zeroed on the aim point (Standard)
Matters when: the group prints above, below, left or right of the aim point at the zero range, and you want that carried to every distance
Depends on: nothing

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[All reference pages](index.md)