The antenna on that GPS was my brother's design. They are still using his
antenna designs 11 years after his death as no one at Garmin has designed
anything better. (he died of cancer at age 63). I remember him describing to me
how he designed that particular helical antenna. We were both EEs and both took
the same fields and waves class from the same hard professor, me 7 years later.
Back when my brother first started designing GPSs, 1980s, it was his third
startup with the other two founders - Garry and Ming = GarMin, the military
dithered the signals to limit the accuracy to something like 100m (or 100Feet
??). They have since relaxed that. The military systems have 10X the bandwidth
and were impressed Garmin could get better accuracy on the commercial system.
So back then, to get survey level accuracy, even with the dither, Garmin had
two units, used the relative distance between them, and was accurate within
inches, if my memory serves me correctly. But it could only do relative
accuracy, not absolute. Not sure what could be done today with relative
distance accuracy without the induced signal dither. Might still be the same.
I am not sure if there is still some level of dither imposed by the military.
With the military system, at 10X the bandwidth, I suspect they can get pretty
accurate. I'm also not sure if Garmin still makes the survey units.
WayneS
At 4/28/2019 11:44 PM, you wrote:
>As previously threatened, I got myself a new GPS. Just picked up a
>Garmin 64ST. Yes, I know it's been surpassed by the 66ST, but the
>price was right in my sweet spot and it actually had better built-in
>trailmaps than the 66ST.
>
>AK Schnozz
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