Back in the old days if you were presented with a reroute when oceanic, you pulled out the charts and plotter and got to work building a new flight plan. If you were good, you could churn out three thousand miles of master document in about fifteen minutes. If you were really good, you had a book of ten degree tables and could cut that time in half.

These days I would just call in the change to my flight planning service and have them fax, e-mail, or just read them to me over the phone. What if you don't have that kind of connectivity or if you just want to be old school for a day?

I haven't seen any published ten degree tables in years. They used to appear in Jeppesen manuals and every now and then you see an abbreviated form. I once worked in a management company for a director of operations who grew up with these tables and often waxed poetic about why they were vital, even today. So, exercising my highest level of OCD, I wrote a set from the equator to 65° latitude (north or south). It took me a week so I kept a copy for myself. You can download a printed set here: True Course 10 Degree Tables.

If you want a step-by-step example, see: International Operations / Reroute.

If required to fly an unplanned oceanic flight plan — you got a reroute just prior to coast out — you need to build a new master document with courses and distances between waypoints so you can still make all the necessary checks before each point and also so you can make your post position plot. The 10 degree tables below provide your true courses and distances between any two positions expressed as latitudes (to the nearest degree) and the next position expressed as a longitude 10 degrees east or west.

For example, say you are 50°N 030°W heading to Europe and your next position will be at 51°N 020°W. You could pull out a plotter and come up with a course, add the variation, and end up with the correct true course. Then you could measure the distance, compare that to the nearest line of longitude and come up with a distance. You would probably do this a few times to make sure you didn't make a mistake, either with the plotter or your ad hoc measuring device. Or you could go to the From 50° Latitude table, check the course provided on the 51° row and Northern Hemisphere / East column and see your true course will be 081° and reading across see that the distance between these two points is 386 nautical miles.

Figure: True Course initial vs. midpoint vs. ending, from Eddie's notes.

The 10 degree tables provide the course at the midpoint between two positions. This will agree with your plotter if you put the center of the compass over the midpoint.

Most FMS (and many flight plans) print the initial course leaving the waypoint. The difference can be significant. When checking your progress, make sure you understand what the FMS is telling your, what you are seeing on the 10 degree table, and what you see with a plotter on a chart.

More about this: Technical / Navigation: Initial vs. Midpoint Course.

To determine the average true course and distance between two points which are ten degrees apart in longitude:

- Find the table with the starting latitude (North or South doesn't matter)
- Find the corresponding latitude in the second column. (If there are two choices, the latitude on top is in the same hemisphere (North or South)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

To determine the average true course and distance between two points which are ten degrees apart in longitude:

- Find the table with the starting latitude (North or South doesn't matter)
- Find the corresponding latitude in the second column. (If there are two choices, the latitude on top is in the same hemisphere (North or South)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

To determine the average true course and distance between two points which are ten degrees apart in longitude:

- Find the table with the starting latitude (North or South doesn't matter)
- Find the corresponding latitude in the second column. (If there are two choices, the latitude on top is in the same hemisphere (North or South)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

- Find the table with the starting latitude (North or South doesn't matter)
- Read the true course underneath the desired hemisphere and direction of travel (east or west)
- Read the distance in the last column

Portions of this page can be found in the book International Flight Operations, Part VIII, Chapter 37.