[amsat-bb] Re: GPS for dx-expedition
Patrick STODDARD (WD9EWK/VA7EWK)
amsat-bb at wd9ewk.net
Wed Sep 1 22:33:02 PDT 2010
> The number of satellites isn’t the main factor in accuracy, it’s the sat
> geometry. A position fix with 4 birds spaced evenly and at a higher altitude
> will give a better position than 8 birds near the horizon bunched around the
> same area of the sky.
I understand that. I was only stating that about the VX-8GR as a
reason why I don't use that device for establishing my location
when working on grid boundaries etc.
When I drove out to the DM23/DM24 grid boundary a couple of
weekends ago, I was able to easily get the VX-8GR and GPSMAP
76S to line up on the grid boundary line (34 degrees North). In fact,
my VX-8GR was chirping away with APRS data on the boundary as
I was taking the photos with the GPSMAP 76S sitting with my radios
for the VUCC documentation (and the QSL cards). I also have a
photo or two of the VX-8GR with 34 degrees North on its display, as
additional proof I was out there.
> That being said, once SA was turned off in 2000, I’ve rarely had a position
> error greater than 20 feet, even with my older Garmin II+. My HCx, easily
> get under 10’ most times.
You're right again. It should be easy to get that 20-foot accuracy,
and this is stated in the VUCC rules. If the GPS is in good
working order, and you're not concerned about having all the latest
bells and whistles, an older GPS is certainly capable of meeting
the VUCC documentation requirements. My GPSMAP 76S is 7
years old, and I don't have any need to replace it. Its firmware
has been updated to the final version released by Garmin before
it was discontinued, and the only thing I have to do with it is
periodically replace the 2 AA batteries that power it.
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