NAVAL SHIP CALIBRATION

Ship radar systems like any front line mobile equipment are susceptible to degradation over time.

 Often other equipment is installed on the ship's superstructure at a later date, introducing unknown adverse shadowing and distortion, resulting in shifts in the angular alignment of the antenna patterns.

Such errors are a serious compromise of the accuracy of the ships defense capabilities.

Simply put, all units must track the same geometrical point in space. The only sure way to accomplish this is to establish an external target location and each sub-system is aligned to the same target. The Fredwal Target provides an ideal point location for the alignment of the parts of a complex defense system.

Ship systems like any Air Defense system consist of multiple units that must be aligned with each other.

Individual systems utilizing internal calibration methods may minimize their own errors but multiple units must align to an external common point in order to eliminate errors between the units.

In order to properly calibrate the suite of radars on a ship it must proceed to a port that contains the proper equipment.

 This is costly as the ship is out of service.

A multiband Fredwal target located on a surveyed point of land, combined with a remote controller aboard the ship, both co-located with integral differential GPS would provide an inexpensive means to calibrate the entire ships radar suite while underway. With several Controllers configured to a variety of ships, every ship in the Navy could be assured of Battle Readiness at a truly negligible cost. Antenna shadowing and superstructure reflections can also be easily mapped, a process that is nearly impossible while in a fixed port location.
 
 Precise calibration requires that both the target location and the radar be known, usually with a survey or other independent means. The ship is a mobile platform, therefore another means of determining its location is required.

The GPS or Global Positioning System is used to fix the location of the target on land,  which can also be surveyed. A second GPS receiver is positioned close to the radar and connected via a data link.

Differential GPS, therefore provides a precise location for the radar in real time. Calibration of the radar can be verified while underway!

If the ship executes a 360 degree turn, while the AGC (automatic gain control) is monitored, the entire ship can be mapped for antenna masking and shadowing.