A few decades ago, companies like AT&T, Ford, IBM, General Electric, Standard Oil, Pan American, J.P. Morgan, and others were making five, ten, even twenty-year plans. The future was predictable. But now companies adjust their plans several times a year and still get shocking surprises. The future is not what it used to be. In many respects, it is no longer predictable. To transmit signals, GPS uses CDMA (Code Division Multiple Access) and GLONASS uses FDMA (Frequency Division Multiple Access). Simply put, all GPS satellites use the same frequency while broadcasting different codes, while GLONASS satellites use the same code but on different frequencies. In previous pages we explained how we had to work harder to make GLONASS as good as GPS for precision applications. Why such a drastic difference between GPS and GLONASS? The answer is that the difference was not drastic until surveyors showed up! When GPS and GLONASS were on the drawing boards, no one had a clue that these systems could be used for millimeter-level accuracy and that the precise community would be potential users. With GPS we just got lucky. With GLONASS we have had to work harder to achieve comparable accuracies.
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