Editing Missile guidance (section)

===Inertial guidance===
{{Main|Inertial guidance}}
[[File:Missile Maintainer inspects missile guidance system of the LGM-30G Minuteman ICBM.jpg|thumb|Inspection of MM III missile guidance system]]
Inertial guidance uses sensitive measurement devices to calculate the location of the missile due to the acceleration put on it after leaving a known position. Early mechanical systems were not very accurate, and required some sort of external adjustment to allow them to hit targets even the size of a city. Modern systems use [[Solid state (electronics)|solid state]] [[ring laser gyro]]s that are accurate to within metres over ranges of 10,000&nbsp;km, and no longer require additional inputs.  Gyroscope development has culminated in the [[Advanced Inertial Reference Sphere|AIRS]] found on the MX missile, allowing for an accuracy of less than 100 m at intercontinental ranges. Many civilian aircraft use inertial guidance using a ring laser gyroscope, which is less accurate than the mechanical systems found in ICBMs, but which provide an inexpensive means of attaining a fairly accurate fix on location (when most airliners such as Boeing's 707 and 747 were designed, GPS was not the widely commercially available means of tracking that it is today). Today guided weapons can use a combination of INS, GPS and radar terrain mapping to achieve extremely high levels of accuracy such as that found in modern cruise missiles.<ref name="zarc"/>

Inertial guidance is most favored for the initial guidance and reentry vehicles of [[Intercontinental ballistic missile|strategic missiles]], because it has no external signal and cannot be [[countermeasure|jammed]].<ref name="ReferenceA"/> Additionally, the relatively low precision of this guidance method is less of an issue for large nuclear warheads.