1. Welcome to the United States Power Squadrons' Chart Smart Seminar
Compass Deviation
(Section 2)

2. The TVMDC Formula  True Course T Variation V Magnetic Course M
Deviation D
Compass Course C 
Add West
Subtract East
Subtract West
Add East
Deviation is different for each boat and depends upon a number of items.
Our class deviation is assumed to be from the Sample Ship's Deviation Table.

3. Select the Deviation for the NEAREST tabulated entry for the Heading
Select the Deviation for the NEAREST tabulated entry for the Heading. For greater accuracy, you may interpolate.
SHIP'S COMPASS HEADINGS
MAGNETIC HEADINGS
USE WHEN CONVERTING TO MAGNETIC
USE WHEN CONVERTING TO COMPASS
Magnetic Heading
Degress
Deviation
Degrees
Compass Heading
Degrees
Deviation
Degrees
000
015
030
045
060
075
090
105
120
135
150
165
180
195
210
225
240
255
270
285
300
315
330
345
5 E
4 W
8 W
11 W
14 W
15 W
12 W
9 W
6 W
3 W
3 E
6 E
9 E
12 E
14 E
15 E
13 E
11 E
8 E
000
015
030
045
060
075
090
105
120
135
150
165
180
195
210
225
240
255
270
285
300
315
330
345
4 E
3 W
6 W
9 W
12 W
14 W
15 W
11 W
8 W
4 W
8 E
12 E
14 E
15 E
13 E
11 E
9 E
7 E
Chart Smart 2002

4. T _____ V _____ M _____ D _____ C _____ 140
Add West
Subtract East
Example #3 notes - deviation is assumed to be from the Sample Ship's Deviation Table (no interpolation); local variation is assumed to be 5 E
5 E
135
Compass course to steer is 147 degrees to make good a true course of 140 degrees
12 W
147

5. T _____ V _____ M _____ D _____ C _____ 204
Add West
Subtract East
Example #4 notes - deviation is assumed to be from the Sample Ship's Deviation Table (interpolate); local variation is assumed to be 11 W
11 W
215
Compass course to steer is 211 degrees to make good a true course of 204 degrees
4 E (interpolation req.)
211

6. End of Section 2D
Compass Deviation