[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)





More information about the Merkaartor mailing list