Re: [NTLK] New GPS Software found?

From: Marco Mailand (Newton2k1_at_mac.com)
Date: Sat Dec 08 2001 - 18:58:43 EST


Am 8.12.2001 17:52 Uhr schrieb "Eric L. Strobel" unter <fyzycyst_at_home.com>:
>>> ... more GIS based
> Nope. GPS is the system of satellites. I forget what the coordinate system
> is called. I want to say WGS-80, but I've got all that info at work.
WGS-84: World Geodetic System, Introduced 1984
There's also a system called W50 or so but it is used mostly in the US and
transfers the ellipsodial grid of the earth to a rectangular projection. It
is also sold in the US as Trimble Map and some GPS receivers (from Trimble
:-) have a built-in conversion. Another similar coordinate system is used
since 1904 in Switzerland. This gives coordinates in meters in positive
numbers only. That's possible with an origin down in France, south-west of
Geneva.
 
>> Differential GPS (dGPS) is one of the more accurate ways to get your
>> coordinates as you are using more satellites
> Nope. dGPS doesn't use more satellites. What it does is compare your
> receiver's information to that of a nearby (usually fixed at a well-known
> datum) GPS receiver. You are able to get a far more accurate relative
> position, as the much of the errors in the positions of the two receivers
> are common -- things like the error introduced by the signals passing thru
> the ionosphere, since the paths are nearly identical, the errors are too.
> By differencing the positions of the two receivers, most of the errors are
> subtracted away.
Very nice description. However, the US DoD deactivated the artificially
introduced satellite signal error some time ago, so that any ordinary GPS
can reach the technically possible accuracy of about 1+/- meter. Of course,
the DoD has the possibilty to activate the error at any time and I don't
know the status now, but I could check it if anyone wants to know it :-)

>> IMO a true GPS handheld is about $6,000 US,
> Good Lord!!! What sort of GPS receiver are you talking about?? I got my
> Magellan for under $100 US on eBay over a year ago.
There's also a so called RTK GPS (real time kinematic) which increases the
accuracy to about 1mm (!) and is used in large construction sites as e.g.
For tunnel drilling, actually south of Zurich. But I doubt that a RTK GPS is
of any special use in Safari hunting :-)

-- 
With best Regards / Viele Gruesse!

Marco Mailand

http://slsbd.psi.ch/timing http://slsbd.psi.ch/~mmailand/ https://www.paypal.com/refer/pal=YYD3VUXUVD2YG

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