Portion of GPS consisting of a network on monitoring stations used to update satellite navigation signals.

A world-wide chain of monitoring and control stations that ensure the accuracy of GPS satellite clocks and their positions.

A world-wide network of GPS monitor and control stations that ensure the accuracy of satellite positions and their clocks.

Means to transfer control information for grouping data segments.

This is a data requirement designator that indicates that the presence of a specified data element is dependent on the value or presence of other data elements in the segment. The condition must be stated and must be able to be processed by a computer

This is a segment that has the same structure as a data segment but is used for transferring control information for grouping data segments. Control segments may be loop control segments (LS/LE), transition set control segments (ST/SE) or functional group control segments (GS/GE), defined in X12.6, or interchange control segments (ISA/IEA/TA), defined in X12.5.

a division of a route within a county, and is almost always measured by city lines