In a military context, especially by the Finnish Non-Linear Artillery of the

Continuation War The Continuation War, also known as the Second Soviet-Finnish War, was a conflict fought by Finland and Nazi Germany against the Soviet Union from 1941 to 1944, as part of World War II.; sv, fortsättningskriget; german: Fortsetzungskrieg. A ...

, the Fire Correction Circle ( fi, korjausympyrä) or (Fire) Correction Converter Dial ( fi, korjausmuunnin) is a fully mechanical auxiliary device which was constructed of

plywood Plywood is a material manufactured from thin layers or "plies" of wood veneer that are glued together with adjacent layers having their wood grain rotated up to 90 degrees to one another. It is an engineered wood from the family of manufactured ...

and transparent plastic and which used to be used to calculate targeting values for non-linear artillery and

mortars Mortar may refer to: * Mortar (weapon), an indirect-fire infantry weapon * Mortar (masonry), a material used to fill the gaps between blocks and bind them together * Mortar and pestle, a tool pair used to crush or grind * Mortar, Bihar, a village i ...

. By using a Correction Circle the

artillery observer An artillery observer, artillery spotter or forward observer (FO) is responsible for directing artillery and mortar fire onto a target. It may be a ''forward air controller'' (FAC) for close air support (CAS) and spotter for naval gunfire su ...

is able to report the necessary fire corrections to the unit firing without knowing exactly where the unit is firing from. This is achieved by having the artillery observer report targets' coordinates and azimuth (from his or her own position) to the firing units, then report corrections (both lateral and distance-) in meters after a salvo. Each firing unit would make their own calculations for correction based on their own position, target's position, artillery observer's

azimuth An azimuth (; from ar, اَلسُّمُوت, as-sumūt, the directions) is an angular measurement in a spherical coordinate system. More specifically, it is the horizontal angle from a cardinal direction, most commonly north. Mathematicall ...

as well as lateral- and distance corrections in meters provided by said observer, in theory allowing for an unlimited number of firing units to fire on a single target using the same target coordinates and corrections reported by a single artillery observer. The system can and is also used to quickly switch between targets within the artillery observer's vision by simply reporting sufficiently large corrections. As an example of this in use, during the

Battle of Tali-Ihantala A battle is an occurrence of combat in warfare between opposing military units of any number or size. A war usually consists of multiple battles. In general, a battle is a military engagement that is well defined in duration, area, and force ...

Finnish Army had 21 artillery battalions and one heavy battery, a total of 250 guns and mortars, focusing their fire on targets inside an area of 7 square kilometers, considered to be a world record at the time.

References

{{reflist Military equipment of World War II Targeting (warfare)