Artillery
However, in the early 21st century, the Global Positioning System (GPS) enabled relatively cheap and accurate guidance for shells and missiles, notably the US 155 mm Excalibur and the 227 mm GMLRS rocket. The introduction of these led to a new issue, the need for very accurate three dimensional target coordinates—the mensuration process.

Weapons covered by the term 'modern artillery' include "cannon" artillery (such as howitzer, mortar, and field gun) and rocket artillery. Certain smaller-caliber mortars are more properly designated small arms rather than artillery, albeit indirect-fire small arms. This term also came to include coastal artillery which traditionally defended coastal areas against seaborne attack and controlled the passage of ships. With the advent of powered flight at the start of the 20th century, artillery also included ground-based anti-aircraft batteries.
The term "artillery" has traditionally not been used for projectiles with internal guidance systems, preferring the term "missilery", though some modern artillery units employ surface-to-surface missiles. Advances in terminal guidance systems for small munitions has allowed large-caliber guided projectiles to be developed, blurring this distinction. See Long Range Precision Fires (LRPF), Joint terminal attack controller

Ammunition: One of the most important roles of logistics is the supply of munitions as a primary type of artillery consumable, their storage (ammunition dump, arsenal, magazine
) and the provision of fuzes, detonators and warheads at the point where artillery troops will assemble the charge, projectile, bomb or shell.
A round of artillery ammunition comprises four components:

Fuze
Projectile
Propellant
Primer

Fuzes: Fuzes are the devices that initiate an artillery projectile, either to detonate its High Explosive (HE) filling or eject its cargo (illuminating flare or smoke canisters being examples). The official military spelling is "fuze". Broadly there are four main types:

impact (including graze and delay)
mechanical time including airburst
proximity sensor including airburst
programmable electronic detonation including airburst
Most artillery fuzes are nose fuzes. However, base fuzes have been used with armor-piercing shells and for squash head (High-Explosive Squash Head (HESH) or High Explosive, Plastic (HEP) anti-tank shells). At least one nuclear shell and its non-nuclear spotting version also used a multi-deck mechanical time fuze fitted into its base.
Impact fuzes were, and in some armies remain, the standard fuze for HE projectiles. Their default action is normally 'superquick', some have had a 'graze' action which allows them to penetrate light cover and others have 'delay'. Delay fuzes allow the shell to penetrate the ground before exploding. Armor or Concrete-Piercing (AP or CP) fuzes are specially hardened. During World War I and later, ricochet fire with delay or graze fuzed HE shells, fired with a flat angle of descent, was used to achieve airburst.
HE shells can be fitted with other fuzes. Airburst fuzes usually have a combined airburst and impact function. However, until the introduction of proximity fuzes, the airburst function was mostly used with cargo munitions—for example, shrapnel, illumination, and smoke. The larger calibers of anti-aircraft artillery are almost always used airburst. Airburst fuzes have to have the fuze length (running time) set on them. This is done just before firing using either a wrench or a fuze setter pre-set to the required fuze length.
Early airburst fuzes used igniferous timers which lasted into the second half of the 20th century. Mechanical time fuzes appeared in the early part of the century. These required a means of powering them. The Thiel mechanism used a spring and escapement (i.e. 'clockwork'), Junghans used centrifugal force and gears, and Dixi used centrifugal force and balls. From about 1980, electronic time fuzes started replacing mechanical ones for use with cargo munitions.
Proximity fuzes have been of two types: photo-electric or radar. The former was not very successful and seems only to have been used with British anti-aircraft artillery 'unrotated projectiles' (rockets) in World War II. Radar proximity fuzes were a big improvement over the mechanical (time) fuzes which they replaced. Mechanical time fuzes required an accurate calculation of their running time, which was affected by non-standard conditions. With HE (requiring a burst 20 to 30 feet (9.1 m) above the ground), if this was very slightly wrong the rounds would either hit the ground or burst too high. Accurate running time was less important with cargo munitions that burst much higher.
The first radar proximity fuzes (perhaps originally codenamed 'VT' and later called Variable Time (VT)) were invented by the British and developed by the US and initially used against aircraft in World War II. Their ground use was delayed for fear of the enemy recovering 'blinds' (artillery shells which failed to detonate) and copying the fuze. The first proximity fuzes were designed to detonate about 30 feet (9.1 m) above the ground. These air-bursts are much more lethal against personnel than ground bursts because they deliver a greater proportion of useful fragments and deliver them into terrain where a prone soldier would be protected from ground bursts.
However, proximity fuzes can suffer premature detonation because of the moisture in heavy rain clouds. This led to 'Controlled Variable Time' (CVT) after World War II. These fuzes have a mechanical timer that switched on the radar about 5 seconds before expected impact, they also detonated on impact.
The proximity fuze emerged on the battlefields of Europe in late December 1944. They have become known as the U.S. Artillery's "Christmas present", and were much appreciated when they arrived during the Battle of the Bulge. They were also used to great effect in anti-aircraft projectiles in the Pacific against kamikaze as well as in Britain against V-1 flying bombs.
Electronic multi-function fuzes started to appear around 1980. Using solid-state electronics they were relatively cheap and reliable, and became the standard fitted fuze in operational ammunition stocks in some western armies. The early versions were often limited to proximity airburst, albeit with height of burst options, and impact. Some offered a go/no-go functional test through the fuze setter.
Later versions introduced induction fuze setting and testing instead of physically placing a fuze setter on the fuze. The latest, such as Junghan's DM84U provide options giving, superquick, delay, a choice of proximity heights of burst, time and a choice of foliage penetration depths.

Projectiles: The projectile is the munition or "bullet" fired downrange. This may be an explosive device. Projectiles have traditionally been classified as "shot" or "shell", the former being solid and the latter having some form of "payload".
Shells can be divided into three configurations: bursting, base ejection or nose ejection. The latter is sometimes called the shrapnel configuration. The most modern is base ejection, which was introduced in World War I. Base and nose ejection are almost always used with airburst fuzes. Bursting shells use various types of fuze depending on the nature of the payload and the tactical need at the time.
Payloads have included:

Bursting: high-explosive, white phosphorus, coloured marker, chemical, nuclear devices; high-explosive anti-tank and canister may be considered special types of bursting shell.
Nose ejection: shrapnel, star, incendiary and flechette (a more modern version of shrapnel).
Base ejection: Dual-Purpose Improved Conventional Munition bomblets, which arm themselves and function after a set number of rotations after having been ejected from the projectile (this produces unexploded sub-munitions, or "duds", which remain dangerous), scatterable mines, illuminating, coloured flare, smoke, incendiary, propaganda, chaff (foil to jam radars) and modern exotics such as electronic payloads and sensor-fuzed munitions.

Stabilization: Rifled: Artillery projectiles have traditionally been spin-stabilised, meaning that they spin in flight so that gyroscopic forces prevent them from tumbling. Spin is induced by gun barrels having rifling, which engages a soft metal band around the projectile, called a "driving band" (UK) or "rotating band" (U.S.). The driving band is usually made of copper, but synthetic materials have been used.
Smoothbore/fin-stabilized: In modern artillery, smoothbore barrels have been used mostly by mortars. These projectiles use fins in the airflow at their rear to maintain correct orientation. The primary benefits over rifled barrels is reduced barrel wear, longer ranges that can be achieved (due to the reduced loss of energy to friction and gas escaping around the projectile via the rifling) and larger explosive cores for a given caliber artillery due to less metal needing to be used to form the case of the projectile because of less force applied to the shell from the non-rifled sides of the barrel of smooth bore guns.