It's in the Charts !

[Mary Farmer]

When I compare a known course between two marks in my cruisers guide to the same two marks in OPEN CPN they are not the same. Off by 10 degrees?

This is the 10 degrees between True North and Magnetic North.
Are there different Charts? Is there some way to charge the orientation?

I'm using charts from:
. Description of NOAA Raster Navigational Charts (NOAA RNCs�)

They look great and have all the nav marks but I would like the info to be the same as the paper charts.

Got any Ideas

[nohal]

Mary...
Which chart exactly? Screenshot? GPX file with the two waypoints?

Pavel

[David M]

Courses are supposed to be labeled as T or M. 180T or 270M for example. Not just a course without that distinction.

The way to convert is to know the variation for the local area.

[svcambria]

Use the magnetic compass rose on the paper charts to measure directions - or change the settings on the electronic display to show true direction...

Michael

[David M]

I think what determines whether it is better to use magnetic or true is your steering compass. Since most yachts use a magnetic compass then I would set all your instruments to magnetic and plot your courses in magnetic in order to be consistent. This will help to reduce navigation mistakes.