Skip to main content

Firefighter Math: 6.5 Declination

The magnetic reference for Earth is north regardless of whether you are traveling north or south. Magnetic declination, or declination, is the difference between the true north reading from the map and the magnetic north reading from a compass. When a compass is used in combination with a map, a correction must be made to allow for declination.

In North America, magnetic declination varies from 30 degrees East in Alaska to 20 degrees West in Labrador, Maine. The degrees of declination for an area are usually located on the bottom margin of the map near the north arrow, or they can be located using a declination chart.declination over the CONUS

The method for correcting for declination is as follows:
1. For Easterly Declination, subtract the declination from the true reading to obtain the magnetic reading. Magnetic = true - easterly declination
2. For Westerly Declination, add the declination to the true reading to obtain the magnetic reading. Magnetic = true + westerly declination

An easy way to remember whether to add or subtract is "West is best and East is least." So for West declination, add to the true reading (West is best, and therefore a larger number) and for East declination subtract from the true reading (East is least, and therefore a smaller number).West is best and east is least

Example 1 - Paloma is in San Jose, California. The declination is 17°E. Paloma's compass reading from her current location to the mountain range to which she is traveling is 35°. What is her true reading?

Step 1. The declination of 17°E is an easterly declination.

Step 2. In this case, True - east = magnetic according to the "East is least" guideline above, so we will solve the equation for the true reading and find that true = magnetic + east. We must add the declination to go from the magnetic reading on the compass to the true reading.

East is least

Paloma's true reading is 52 degrees.

Example 2 - Sonia is in Augusta, Maine. She has a compass with a magnetic north reading of 45°. What is her true reading on a map?

Step 1. Look up the declination for Augusta, Maine, on a declination chart. Maine has a declination of 18°W.

Step 2. Because 18°W is a westerly declination, remember "West is best" and that the magnetic = true + west. In this case, to solve for the true reading, we must subtract the declination from the magnetic bearing: true = magnetic - west.

west is best

Sonia's true reading is 27 degrees.

When traveling in an opposite direction and adjusting map readings for use with compass readings, do the opposite of the above for adding and subtracting the declination. 

Example 3 - Roger looks at a map and takes an azimuth reading of 85°, a true reading, off the map from where he is standing to the location of a tower. The declination for the area is 12°E. What is the magnetic reading?

Step 1. In order to find the magnetic reading by using a compass, subtract the easterly declination. Remember, "East is least."

85° - 12°= 73°

Roger's magnetic reading is 73 degrees.

 

NWCG Latest Announcements

2024 Paul Gleason Award Winners Announced

Date:  March 13, 2026
Questions? 
Please contact: Leadership Committee

The NWCG Leadership Committee is proud to announce the recipients of the 2024 Paul Gleason "Lead By Example" awards. Award categories include Initiative and Innovation, Mentoring and Teamwork, Motivation and Vision, as well as a Lifetime Achievement Award.

Congratulations to the awardees:

  • Justin Baxter, National Unmanned Aerial System (UAS) Operations Specialist, with the U.S. Forest Service — Initiative and Innovation
  • Kelly Woods, Director of the Wildland Firefighting Lessons Learned Center — Mentoring and Teamwork
  • Doug Booster, Instructor, ProHealth Net, Inc. — Motivation and Vision
  • Pam McDonald, Writer-Editor for the National Interagency Fire Center — Lifetime Achievement Award

References:

Paul Gleason Lead By Example Award

Wildland Fire Leadership Development Program (WFLDP)

Leadership Committee

NEW! S-231, Engine Boss Course Available Now

Date:  March 6, 2026
Questions? 
Please contact: Incident Operations Subcommittee

NWCG is pleased to announce the new S-231, Engine Boss (Single Resource) course is now available on the Wildland Fire Learning Portal (WFLP). Developed through the Incident Performance and Training Modernization (IPTM) effort, this training supports individuals working towards Engine Boss, Single Resource (ENGB) incident qualifications. 

This is a performance-based instructor-led training (ILT) that focuses on the application of ENGB responsibilities during wildland fire operations, emphasizing readiness, information gathering, risk management, engine tactics, and Wildland Urban Interface (WUI) operations. Trainees apply these skills through scenario-based group work and an optional field day that reinforces hands-on engine operation tasks. 

References:

S-231, Engine Boss (Single Resource) (Instructor-led)

NWCG Engine Boss, Single Resource (ENGB) Position Page

Wildland Fire Learning Portal

NWCG Celebrates 50 Years!

Date:  March 6, 2026
Questions? 
Please contact: NWCG Executive Secretary

NWCG is proud to celebrate 50 years of service to the wildland fire community. Beginning in 1976 with an interagency agreement between the Department of Interior and Department of Agriculture, NWCG has grown to include additional member agencies and is recognized as the standard-setting leader in wildland fire operations.

To honor where we’ve been and highlight where we are going, the NWCG team has created a video showcasing our history and accomplishments. The video is now available on the NWCG website.

References:

NWCG 50 Year Anniversary Video

NEW! S-131, Firefighter Type 1 Course Available Now

Date:  March 6, 2026
Questions? 
Please contact: Incident Operations Subcommittee

NWCG is pleased to announce the new S-131, Firefighter Type 1 course is now available on the Wildland Fire Learning Portal (WFLP). Developed through the Incident Performance and Training Modernization (IPTM) effort, this course is a performance-based instructor-led training (ILT) that focuses on the application of situational awareness and decision making, building on the knowledge and concepts introduced in previous required courses. Using a threaded fictitious fire, each unit focuses on a performance-based activity in which students practice applying their decision-making and problem-solving skills.

The S-131, Firefighter Type 1 course is required for individuals seeking qualifications to be a Firefighter Type 1 (Squad Boss) (FFT1) or an Incident Commander Type 5 (ICT5).

References:

S-131, Firefighter Type 1 (Instructor-led)

NWCG Firefighter Type 1 (Squad Boss) Position Page

NWCG Incident Commander Type 5 Position Page

Wildland Fire Learning Portal