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    Re: Origins of civilian use of GPS
    From: Peter Monta
    Date: 2018 Jul 6, 08:58 -0700
    > Many recent articles and books claim that GPS was a military only system prior to the shooting down of KAL007.  I discuss this in a recent article.

    As you know, surveyors and geodesists were also very early with civilian use of the system, in particular with carrier-phase modes, codeless and semicodeless L2, and precise orbits.  While this was not real-time navigation, it was still a significant civilian use, so there must have been some awareness at the time that such use was possible.

    You mention Transit in your article:  whether it was 2D or 3D depends on the use case.  For a single pass, yes, height is roughly degenerate with longitude, so you need to fix the antenna height.  But with multiple passes (which will take at least a few hours), a full 3D position is possible.  If the Transit constellation had been larger, say a dozen or so satellites per plane, it would have been a near-real-time 3D system.

    Cheers,
    Peter

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