redshift schreef :
Vandaar dat de aangehaalde UBlox het in auto's lees hoge snelheid prima doet ( doen ze allemaal trouwens) de invloed van een afwijking van de tussen liggende posities wordt bij toenemende snelheid steeds minder belangrijk, door de grotere afstand tussen de punten. Bij lage snelheid heeft deze afwijking een enorme invloed op de COG en SOG.
Ook autos kunnen langzaam gaan. Daarbij gaat de COG echt niet wild varieren. Ublox (en ook andere state of the art) GPS modules zijn al zo nauwkeurig dat ook bij lage snelheid de COG nog redelijk stabiel blijft. Als de SOG kleiner dan 0 wordt, geeft de Ublox geen COG meer af. Het COG veld in de NMEA zin blijft dan leeg.
Vanmiddag voor de gein op weg naar Ma Belle in de rubber dinghy een testje gedaan met Ublox GPS en data logger. De dinghy danste behoorlijk op de golfjes (wind tegen tij). De GPS lag op de bodem op z'n kant in een tas. Snelheid: rond 2 knopen (4 knopen STW, 2 kn tij). Zoals te zien is in de NMEA output, waren 12 Satellieten in gebruik en bleef de HDOP onder 1. SOG rond 2 kn., soms wat afgeremd door golfjes. De COG schommelt wat rond 90 gr. maar dit is een direct gevolg van het sturen met bb motor. Geen grote sprongen dus, en dit is zonder enige filtering.
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