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6.7 Closed Traverse

A closed traverse is a series of connected lines whose lengths and bearings are measured off these lines (or sides), which enclose an area. A closed traverse can be used to show the shape of the perimeter of a fire or burn area. If you were to pace continuously along the sides of a closed traverse, the finishing point would be the same as the starting location.

Note in the following sketch how the traverse is followed clockwise. If the direction was followed counterclockwise at any point, the bearing letters would change to their opposites but the numbers would not, as shown in the first sketch (1) below. The second sketch (2) is a closed traverse. Here, the series of lines completes a distance area, and the starting and ending points are the same.
 

Traverse Examples

Example 1 - Jeff paced the perimeter of the Zavala fire. His pace is 13 paces/chain. The declination for his current location is 14.5°E. The direction, distance, and travel for Jeff is as follows: Jeff begins at point 1 and goes N42°W for 27 paces; from point 2 he goes N75°W for 16-1/2 paces; from point 3 he goes N31°W for 24-1/2 paces; from point 4 he goes N36°E for 29-1/2 paces; from point 5 he goes S65°E for 22 paces; from point 6 he goes S13°E for 52-1/2 paces; from point 7 he goes S21°W for 10-1/4 paces back to the starting point, point 1.

Convert the bearings to magnetic readings. Adjust the magnetic readings to true north readings. Plot the closed traverse in feet using an engineer's tenth ruler and protractor.

Step 1. Convert paces into feet. Jeff's pace is 13 paces per chain. Set up the cancellation table (Section 2.1) and solve for distance in feet.

cancellation table
Repeat this step for each distance.

Step 2. Convert the bearings to magnetic readings. See Section 6.1.

The NW quadrant is between 270° and 360°. 360° - 42° = 318° 
The SE quadrant is between 90° and 180°. 180° - 65° = 115°
The NE quadrant is between 0° and 90° so those values are used as recorded.
The SW quadrant is between 180° and 270°. 180° + 21° = 201°

The resulting magnetic reading are listed in the table below. 

Step 3. Adjust each magnetic reading to a true reading following the guidelines in Section 6.5.

Closed Traverse

Step 4. Choose a scale. 1/10 inch = 10 feet

Step 5. Using a protractor (angles measured in degrees) and an engineer's scale or tenth's ruler, plot the plan view of the traverse horizontal distance (feet) and the bearing (degrees) between points.

image of protractor measuring angles

image of engineer's rule

Step 5a. Set the protractor so the 0°/180°line is up (north) and on a north-south axis.

Step 5b. Put a point in the middle hole. This will be point 1.

Step 5c. Read 318° on the outer scale of the protractor.
Put a dot to mark the point.

index point on protractor


Step 5d. Draw a line from point 1 up to the dot that is 13-7/10 marks (each inch has 10 marks).

ruler with points

Step 5e. The end of this line will be point 2. Put the hole of the protractor on point 2. Follow steps 5b and 5c with each of the values.

When plotting the values that are in the southern quadrants with a semicircle protractor, rotate the protractor so the 0°/180°line is down (facing south) and read the numbers on the inner scale. Continue to complete all the points. The end result should be a closed traverse as shown.

Step 5f. Convert the true readings to bearings. 

P1 to P2 = 360° - 332.5° = N27.5°W
P2 to P3 = 360° - 299.5° = N60.5°W
P3 to P4 = 360° - 343.5° = N16.5°W
P4 to P5 = 0° + 50.5° = N50.5°E
P5 to P6 = 180° - 129.5° = S50.5°E
P6 to P7 = 181.5° - 180° = S1.5°E
P7 to P1 = 215.5° - 180° = S35.5°W

Label the lines of the traverse with the corresponding bearings.

 

NWCG Latest Announcements

Updated NWCG Standards for Water Scooping Operations, PMS 518

Date: December 19, 2024
Contact: Water Scooper Operations Unit

The NWCG Standards for Water Scooping Operations, PMS 518 establishes the standards for dispatching, utilizing, and coordinating water scooping aircraft on interagency wildland fires. These standards should be used in conjunction with the NWCG Standards for Aerial Supervision (SAS), PMS 505, and any local, state, or geographic/regional water scooping plans.

References:

NWCG Standards for Water Scooping Operations, PMS 518

Updated NWCG Standards for Aerial Supervision, PMS 505

Date: December 19, 2024
Contact: Interagency Aerial Supervision Subcommittee

The Interagency Aerial Supervision Subcommittee has updated the NWCG Standards for Aerial Supervision, PMS 505. PMS 505 establishes standards for aerial supervision operations for national interagency wildland fire operations. 

References:

NWCG Standards for Aerial Supervision, PMS 505

New Job Aids Available: Packing Lists for Wildland Fire Fireline Personnel and Support Staff, J-101 and J-102

Date: December 3, 2024
Contact: NWCG TRAINING

Two new job aids are now available: Packing List for Wildland Fire Fireline Personnel, J-101 and Packing List for Wildland Fire Support Personnel, J-102, should serve as a baseline for items needed on a wildland fire assignment. These lists will help personnel prepare for a 14 to 21-day assignment on the fireline or in a support role.

References:

Job Aid Catalog

NWCG Packing List for Wildland Fire Fireline Personnel, J-101

NWCG Packing List for Wildland Fire Support Staff, J-102

NWCG Equipment Technology Committee Releases Safety Warning: 24-001 Stihl Chainsaw Toolless Fuel Cap Spill Prevention

Date: November 14, 2024
Contact: Equipment Technology Committee

The Equipment Technology Committee (ETC) has released Safety Warning: 24-001 Stihl Chainsaw Toolless Fuel Cap Spill Prevention. Misaligned toolless fuel caps on Stihl chainsaws have led to recurring fuel spillage, fuel ignition, and burn injuries during wildland fire management operations.

This Safety Warning is intended to highlight the details and recommended procedures for the installation of a Stihl chainsaw toolless fuel cap, as well as how to identify and correct a misaligned, damaged, or broken fuel cap to help prevent fuel spillage.

References:

NWCG Safety Warning: 24-001 Stihl Chainsaw Toolless Fuel Cap Spill Prevention

Advertencia de equipos 24-001: Prevención de derrames de la tapa de combustible sin herramientas de la motosierra Stihl

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