NavList:

I just received an email from Ocean Navigator that contains an article by David Berson with a "navigational problem" that uses the sunrise tables in the NA in reverse to determine Longitude.  Basically given a decent DR Latitude you compute the time of sunrise at that latitude and take the time difference between the computed sunrise and the actual sunrise and convert that into a longitude factor (using time to arc) with which you can then derive Longitude.

 

While in theory this is a great method, it doesn't seem very accurate in practice.  My calculations for sunrise and sunset can be off by several minutes.  The variable and considerable refraction of the sun at the visible horizon would lead me to believe that there would need to be considerable corrections applied which don't appear in David's example

 

Does anyone know of any real-world data with this method to provide an expected range of error?  This seems an emergency method only, but I'd be interested to know if anyone has tried it, or heard of anyone who has.

 

Here is the long URL for the article:

 

As an aside, this fellow lives but 15 minutes from me, and I've never met him.  I really should try to meet up with the guy since we have a shared interest.

 

Jeremy