GEOG 862
GPS and GNSS for Geospatial Professionals

Summary of C/A, L2C, and L5

GPS Signal Modernization illustration, described in text below. Present signal (Block II/IIA/IIR), M, 2nd  Civil Block IIR-M, IIF, 3rd Civil Block IIF
GPS Signal Modernization
Source: GPS for Land Surveyors: (Adapted from Steve Lazar, Crosslink (Summer 2002), Aerospace Corporation.

GPS modernization is underway. New spacecraft with better electronics, better navigation messages, newer and better clocks are just part of the story. Beginning with the launch of the first IIR-M satellite, new civil sig­nals began to appear, starting with L2C which was followed by L5 on the Block IIF satellites.

These signals tend to have longer codes, faster chipping rates, and more power than the C/A and P(Y) codes have. In practical terms, these developments lead to faster first acquisition, better separation between codes, reduced multipath and better cross-correlation properties.

The legacy L1 and L2 signals are at the top of the illustration. In the next tier, you see the L1 with the addition of the M-Code and substantially the same otherwise. L2 has both the M-Code and the new L2C Civilian code. In the third tier and the Block IIF satellites, there is the addition of L5.