Differential GPS

> > What I don't understand is how they are claiming accuracy within

> A point in the close vicinity, at Lat X Long Y Height Z gets told via

- by using the fixed value of the DGPS broadcast point, accuracies
improved
substantially - the value dropped off the moment the dither factor was
lifted - still usefull under very bad weather conditions but otherwise
expensive and bulky woth no current value.... (a standard GPS needs additional
reciever hardware to pick up dgps broadcasts).

The highly esteemed Brendan Pratt (winner of Full Thrust competitions
> too numerous to mention) wrote:

> - by using the fixed value of the DGPS broadcast point, accuracies

Jeez, you stop doing military work for a few years and see what happens.

I bust a gut making sure I only give the general theory, with no Classy

Brendan Pratt schrieb:
> - by using the fixed value of the DGPS broadcast point,

One of the uses of DGPS is in container terminals at harbours. The carrier
vehicles that move the containers about are tracked with the help of their
DGPS systems. This allows to keep track of the positions of all the containers
on the terminal. To do this, the accuracy must be less than the width of a
container (8 feet).

Greetings

> One of the uses of DGPS is in container terminals at harbours. The

I use a non-dgps unit to mark positions of Flathead schools on the
bottom
during drift fishing - accuracy needs to be about 3-6 feet which is
perfectly achievable with a good civilian model now that the dither factor
is gone - previously I would have needed to invest in an AUD $600
decoder to attach to my hand held gps to get that level of accuracy. Customs
in Melbourne use the system you described as well as several taxi and armoured
car companies in Sydney - the potential usage base is enourmous - most
of
which could not occur were the US govt to re-establish the limiters that
were originally installed (Yay ex-pres. Clinton! ).

> Jeez, you stop doing military work for a few years and see what

Stop - my already enourmous ego is threatening to annex Poland.....

> Ah for the good old days of Satnav and Sextant (good name for a game
Avast there, Shiver me timbers, and Where Be the Poop Deck.
> (The Poop Deck be below the Crow's nest, that's why it do be called

- Yipe - those days also saw the use of open air amputations and
involuntary
recruitment - I've always disputed the phrase "good ol' days".

With DGPS for Aviation use they have been touting centimeter accuracy.

Magic

> --- KH.Ranitzsch@t-online.de wrote:

> One of the uses of DGPS is in container terminals at

> With DGPS for Aviation use they have been touting

Yup - POTENTIAL accuracy - not average accuracy  - I have a techie from
NAVMAN with me as I write this, there are many contributing factors to the
precision of a GPS with or without DGPS - the beacons do improve
accuracy, but only limiting the margin of error to about 1 metre otherwise,
most civilian units will achieve this some of the time but will range around 5
metres most of the time :-)
Now I have to go and sell Richard a fishing licence....

Brendan,

Interesting stuff.  They are talking about 3-D
accuracy to a meter and with a DGPS unit at the airport you are going getting
the error to less than a centimeter at touchdown.

I will be happy to see it as some approaches into the fog to get home have
been quite dicey. 50 ft hover with no ground in site!

Magic

> --- Brendan Pratt <bastard@oalink.com.au> wrote:

> Yup - POTENTIAL accuracy - not average accuracy - I

> Interesting stuff. They are talking about 3-D

probably have mutiple transmitters arrayed around the area (on hills and
towers etc.) - but they still don't land using GPS - nor would I want to
do so with the degree of variability you can get from even a DGPS unit from
second to second - did you know that Europe has their own series of GPS
satellites? EGNOS is due to be online in 2003 and promises and accuracy of 9
metres 95% ofthe time (still want to use this for anything precise) -
the WAAS and EGNOS netorks are good, DGPS helps greatly at close range but the
system become truely cool when you have the latest satellite
co-ordinates
and the lag time decryption codes :_)

> I will be happy to see it as some approaches into the

Yup and a ground controller with a bleeding ulcer and a substance abuse
problem telling him to ignore the GPS and follow the route on screen -
"what
mountain? don't you trust me? Listen I've been doingthis for years? no -
I'm not bitterand twisted..." Paranoia notwithstanding GPS is cool and make my
life easier and your life safer but practical experience demand we avoid as
much industry
"information" as possible - they're not always giving us the whole
story.

Good Points.

For me GPS+ILS+Radar(Ground Control and organic to
helo)+Radar Altimeter+LocalKnowledge+Skill+Luck+Prayer
all have so far brought me home. I will continue to bet my life on this
combination and continue to hope for improvements in all!

Bob

> --- Brendan Pratt <bastard@oalink.com.au> wrote: