[Merkaartor] Various GPS issues
Dirk Stöcker
openstreetmap at dstoecker.de
Tue Aug 18 15:54:17 BST 2009
On Tue, 18 Aug 2009, Stefan Dirsch wrote:
> You're right. Speed isn't calculated neither by the timestamps in the NMEA
> records themselves nor by the current time when the NMEA record is received
> from gpsd, but taken from the seperate field. Sorry for the confusion.
Actually this is part of my job, that's why I asked. Theoretically the
speed value should be more accurate than position itself as it is (very
likely) taken from Doppler measurement (and afterwards filtered which
removes short-term effects and probably invalidates previous statement
:-).
Maybe there is a conversion error somewhere? The RMC data in the example
has speed in knots and not km/h.
P.S. Note my text having many vague statements. This is due to the
black-box character of many GPS devices.
Ciao
--
http://www.dstoecker.eu/ (PGP key available)
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