The World's Most Advanced Sailing Education and Sailing Certifications

HDG MAG = Compass heading or Magnetic Heading (with deviation removed)

Forum - Coastal Navigation - HDG MAG = Compass heading or Magnetic Heading (with deviation removed)
Module Content - Sea Talks2
avatar
Student
Conan Hom
Lexington, MA, USA
Crew Level 0
Status: Sailor
Qualified days: 8
HDG MAG = Compass heading or Magnetic Heading (with deviation removed)
Posted 2016, Nov 08 03:42
Does HDG MAG in the table = (1) compass heading of the ship or does it mean (2) the magnetic heading (with deviation removed)? It would seem to me problematic if it were (2) because the ships compass doesn't given you the magnetic heading and you have no way of directly measuring the magnetic heading to determine the deviation. Futhermore, in the example, why does one compensate for deviation on a HAND HELD (caps for emphasis) compass reading since in the previous section on deviation it was stated that hand held compasses are less affected than the ship's compass?
Add reply
0 0

Replies

avatar
Student
Conan Hom
Lexington, MA, USA
Crew Level 0
Status: Sailor
Qualified days: 8
Reply 2016, Nov 10 05:17
So to summarize your answer HDG MAG = compass heading however I'm still puzzled why in the example, the hand held compass reading was still corrected for deviation (based on what the module said about the hand held compasses not being affected by deviation).
0 0
avatar
Administrator
Grant Headifen
Reply 2016, Nov 10 14:13
No - the magnetic heading does not equal the compass reading. Compass must be corrected using the table. You asked if on the table - do you use compass reading or magnetic heading to input to the table to find the deviation. My answer was that the actual deviation using either would give you a very similar answer. i.e. determine the deviation using 270 degrees - now determine the deviation using 272 say by interpolating. They both will arrive at the same answer for deviation within tenths of a degree. Now take that deviation which will be several degrees and apply to the correction.
0 0
1 - 2 of 2 replys

Add reply

* - required fields

Please signin first
Add your reply in a positive and constructive manner and tone. Be as specific and clear as possible. Other students will vote your reply up or down depending on its usefulness the clarity. Your comments are always editable.