A system for post-processing global navigation satellite system, GNSS, data to enhance position accuracy, comprising: a processor; memory storing a GNSS data file; a first set of code executed by the processor to provide a position, velocity, and time, PVT, application, wherein the PVT application processes the GNSS data file with a forward run to generate a first forward run position file; a second set of code executed by the processor to provide a mirror time application modifying the GNSS data file to generate a mirrored GNSS data file, wherein the mirrored GNSS data file comprises measurement epochs of the GNSS data file in reverse order, and wherein the PVT application processes the mirrored GNSS data file with a forward run to generate a second forward run position file, wherein the mirror time application modifies measurements read from the GNSS data file to form mirrored measurements in the mirrored GNSS data file including, for each of the reverse order measurement epochs, modifying range and phase by a difference between calculated distances at a first epoch and a second epoch, the second epoch being the reverse order measurement epoch of the first epoch, and modifying doppler by a difference between calculated velocities at the first epoch and the second epoch such that residuals associated with the GNSS data file at each of the measurement epochs match residuals associated with the mirrored GNSS data file at each of the reverse order measurement epochs; and a third set of code executed by the processor to provide a combiner application combining the first and second forward run position files to generate a precise position file including position data with higher accuracy at one or more epochs than in only one of the first and second forward run position files, wherein the mirror time application mirrors orbit data provided in the mirrored GNSS data file by modifying ephemeris in the GNSS data file such that a satellite associated with data in the GNSS data file is flying backwards based on its satellite positions. a processor; memory storing a GNSS data file; a first set of code executed by the processor to provide a position, velocity, and time, PVT, application, wherein the PVT application processes the GNSS data file with a forward run to generate a first forward run position file; a second set of code executed by the processor to provide a mirror time application modifying the GNSS data file to generate a mirrored GNSS data file, wherein the mirrored GNSS data file comprises measurement epochs of the GNSS data file in reverse order, and wherein the PVT application processes the mirrored GNSS data file with a forward run to generate a second forward run position file, wherein the mirror time application modifies measurements read from the GNSS data file to form mirrored measurements in the mirrored GNSS data file including, for each of the reverse order measurement epochs, modifying range and phase by a difference between calculated distances at a first epoch and a second epoch, the second epoch being the reverse order measurement epoch of the first epoch, and modifying doppler by a difference between calculated velocities at the first epoch and the second epoch such that residuals associated with the GNSS data file at each of the measurement epochs match residuals associated with the mirrored GNSS data file at each of the reverse order measurement epochs; and a third set of code executed by the processor to provide a combiner application combining the first and second forward run position files to generate a precise position file including position data with higher accuracy at one or more epochs than in only one of the first and second forward run position files, wherein the mirror time application mirrors orbit data provided in the mirrored GNSS data file by modifying ephemeris in the GNSS data file such that a satellite associated with data in the GNSS data file is flying backwards based on its satellite positions.