From: Bill Kealey (cwkealey@atlanticbb.net)
Date: Wed Dec 21 2005 - 13:42:26 PST
>I sure would like to know where you all are getting the high speed stuff to
>give such good coordinates........in the military (as I am and have been
>for 18 years) we can only get as close as 10 feet. If you all can send the
>updated codes I would gladly use them ........then again I am a Marine and
>should probably check with the AF or the Navy to get the good
>stuff......ours will probably come to age when you all get the "new" stuff.
>
> ......but still wondering how you all get to 1 foot?????
>
>
>
> SSGT SMITH CN
> USMC MITT, 1ST BN, 3RD BDE, 7TH DIV
> NUMANIYAH
> APO AE 09331
>
> M880, M274A5, 6K GenSet
Cliff,
I was always told that the best my unit could expect to do on a good day was
about 3' or 1 meter. Playing around in the police boats and pilings that
are usually considered "fixed objects" I found that the accuracy was, as you
said more like 10' to 12' or approximately 3 meters.
My GPS altitude readings are so far off that I have never found them to be
useful to me. When I lived near and worked on Chesapeake Bay, altitude was
never an issue. We didn't get any tsunamis that I recall so basically the
tidal difference was all I had to adjust for and did not need GPS for that.
I am now with the local fire department in the mountains and the altitude
readings could be very helpful with Search and Rescue here with the use of
topo maps. Again, the unit that I use shows it is rarely more accurate
then within +/- 185 feet or so. I am situated in a valley between two small
mountains with a third splitting them about a half mile or so from my home.
I know that our engineering division used to have to hook up two antennas to
the GPS and separate the antennas about 4 or 5 feet to get accuracy good
enough to be useful in court and it did work. They were using the same
Garmin 45 at that time that I use now. Again, that was at least 10 years
ago so I know that the technology has improved quite a bit.
I certainly would not want to use my GPS unit to do an accurate survey of my
property line (or say, a mine field) but would have no problem using it as a
reference tool.
And, to put the accuracy in a different perspective, how much compensation
does one allow for the width of a pencil point when locating your position
on a map/chart? This can certainly open another can of worms as pencil
points vary quite a bit depending on many factors such as, the sharpener
used, how long between sharpenings you have been using it, diameter of lead
used if a mechanical pencil and other things. We also have to compensate
for the proportional size of the map/chart being used.
So, IMHO, unless the GPS units are that much more accurate than what I have
been using all these years I personally doubt that the units are normally as
accurate as advertised. However, anything is possible.
Have a great day.
Bill K.
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