Seaclear software and COG

[mikebutler]

Noticed something strange over the weekend. I use seaclear on a PC, I also have a chart plotter next to the helm & a handheld GPS. The chart plotter & handheld gps both gave the same Course over the Ground but the PC program gave about 10 degrees less! I then connected the handheld to the computer and again seaclear gave a reading of about 10 degrees less. Anyone else had this problem?

 

[jeremyshaw]

Only logical explanation I can think of is that two of your instruments are reporting magnetic and one is reporting true...