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Firefighter Math: 6.8 Intersection

Intersection is a method of locating a point on a map by intersecting lines from two known landmarks on the ground. Intersection is one method fire lookouts use in determining the location of a fire. The procedure is as follows:

  1. From the first position, point 1, take a compass reading of the object or fire.
  2. Adjust for declination.
  3. With a compass or protractor, plot this azimuth on the map.
  4. Draw a line from point 1 beyond the point of the object or fire.
  5. Move down the road to a second position, or radio to the second person's location and get that azimuth reading. Repeat steps 2 through 4.
  6. A third and maybe a fourth reading will help further describe the location.
  7. The object or fire is located where the individual lines cross.

Example 1 - Tom is at a lookout tower at point A. He spots a fire and takes a compass reading. The magnetic azimuth is 277°. He radios to John at tower B, who tells him his magnetic azimuth on the fire is 337°. The declination for the area is 16°E. Plot the lines to find the location of the fire. 

Step 1. Convert the magnetic azimuths to true azimuths by adjusting for declination (see Section 6.5).
277° + 16° = 293°
337°+ 16°= 353°

Step 2. Draw the lines of the azimuth from each point well past the fire.

2 lines crossing

Step 3. Read where the two lines intersect to get the location of the fire.

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NWCG is excited to announce that S-320, Introduction to Incident Management Teams (Blended) is now available on the Wildland Fire Learning Portal!

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NWCG is excited to announce the release of the new Ransom Road Fire Module to RT-130, Wildland Fire Safety Training Annual Refresher (WFSTAR).

This module features a firsthand account from Rob Lee, official reports, and animated maps of the Ransom Road Fire which occurred on June 8, 1981, in Florida's Merritt Island National Wildlife Refuge.

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Call for Nominations: Paul Gleason Lead by Example Award

Date: December 11, 2025
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Do you know someone working in wildland fire who strives to make positive change and is undeterred by obstacles or setbacks? Now is your chance to give that person the acknowledgment they deserve by nominating them for a Paul Gleason Lead by Example Award.

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Coming Soon! Ransom Road WFSTAR Module

Date: December 9, 2025
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On June 8, 1981, the Ransom Road Fire swept across Merritt Island National Wildlife Refuge in Florida, marking a defining moment in wildland fire management. This event led directly to the creation of the U.S. Fish and Wildlife Service's professional fire program.

Later this month, NWCG will release a compelling video that brings the Ransom Road Fire to life through firsthand accounts, official reports, and animated maps. Rob Lee, second on site during the deployment, shares his powerful recollections of that day. 

This video will be going live later this month in NWCG's RT-130, Wildland Fire Safety Training Annual Refresher (WFSTAR) Catalogue.

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