ADR Sign Convention used in NovAtel GPS Receivers and RINEX
All NovAtel GPS receivers output ADR (Accumulated Doppler Range) with a "-" (minus) sign. This is an arbitrary convention adopted many years ago (circa 1992 on the first PC1/OEM1 GPS boards). The carrier phase (ADR) is always arbitrary and the sign of the carrier phase is irrelevant, as long as delta-carrier-phase is consistent until the next lock break. RINEX standards and specifications require a positive ADR value such that the PSR (pseudorange) and ADR will have the same, positive sign. Thus, NovAtel's Convert software tool will remove the minus sign from the ADR when used to convert NovAtel raw measurement data into the standardized RINEX format. This ADR sign convention is not a problem when the original, raw measurement data is directly post processed using the GrafNav post processing software.