"Jens Bruun" <bruun_jens@hotmail.com> skrev i en meddelelse
news:bl6fce$2100$2@news.cybercity.dk...
> "Tom" <tom_christensen@bigfoot.com> skrev i en meddelelse
> news:3f7691b0$0$48903$edfadb0f@dtext02.news.tele.dk...
>
> > Endeligt kan man jo vælge at bruge hjælp fra radiofyr som kan få
> > nøjagtigheden ned på et par meter, men det er ikke mit indtryk at
> DANSKE
> > taxa'er bruger fyr til hjælp. Jeg ved faktisk heller ikke hvor udbredt
> disse
> > radiofyr er i danmark, men i usa bruges det i stor udstrækning.
>
> DGPS? Er vel strengt taget ikke nødvendigt længere, da amerikanerne ikke
> længere "scrambler" signalet.
Jeg tænker på WAAS
Lidt citat:
WAAS and its Relation to Enabled Hand-Held GPS Receivers
(26 Feb. 2003)
Statement from the FAA
WAAS is based on a network of approximately 25 ground
reference stations
that covers a very large service area. Signals from GPS
satellites are received by
wide area ground reference stations (WRSs). Each of these
precisely surveyed
reference stations receive GPS signals and determine if
any errors exist. These
WRSs are linked to form the U.S. WAAS network. Each WRS in
the network
relays the data to the wide area master station (WMS)
where correction
information is computed. The WMS calculates correction
algorithms and assesses
the integrity of the system. A correction message is
prepared and uplinked to a
geosynchronous satellite via a ground uplink system (GUS).
The message is then
broadcast from the satellite on the same frequency as GPS
(L1, 1575.42MHz) to
receivers on board aircraft (or hand-held receivers) which
are within the broadcast
coverage area of the WAAS. These communications satellites
also act as additional
navigation satellites for the aircraft, thus, providing
additional navigation signals for
position determination.
The WAAS will improve basic GPS accuracy to approximately
7 meters vertically
and horizontally, improve system availability through the
use of geostationary
communication satellites (GEOs) carrying navigation
payloads, and to provide
important integrity information about the entire GPS
constellation.
--
Tom
Unofficial FORD site Denmark
http://members.tripod.com/FORD_DK