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5.2 Map Scale

The map scale is printed in the map legend. It is given as a ratio of inches on the map corresponding to inches, feet, or miles on the ground. For example, a map scale indicating a ratio of 1:24,000 (in/in), means that for every 1 inch on the map, 24,000 inches have been covered on the ground. Ground distances on maps are usually given in feet or miles. 
 

Map Scale Conversion Factors

 

Scale Representative Fraction Map in/mi Map in/ch map ft/in
1:253,440 253.44 0.25 0.0031 21,120
1:126,720 126.72 0.50 0.0063 10,560
1:63,360 63.36 1.00 0.0125 5,280
1:62,500 62.50 1.01 0.0127 5,208
1:31,680 31.68 2 0.025 2,640
1:24,000 24.00 2.64 0.033 2,000
1:21,120 21.12 3 0.038 1,760
1:15,840 15.84 4 0.05 1,320
1:7,920 7.92 8 0.1 660

Table 5.1. Map Scale Conversion Factors

Example 1 - Convert the map scale of 1:24,000 (in/in) to (in/ft).

Step 1. Set up the cancellation table so all units will cancel, except the desired unit, ft/in.

cancellation table

On the map 1 inch is equal to 2,000 feet on the ground, 1:2,000 (in/ft).

Example 2 - Convert the 1:2,000 (in/ft) to (in/mile).

Step 1. Set up the cancellation table so all units will cancel, except the desired unit, miles/inch.

cancellation table

On the map 1 inch is equal to 0.4 miles.

Example 3a - The map distance between two points is 6 inches. The map scale is 1:24,000 (in/in). What is the ground distance in feet?

Set up the cancellation table so all units will cancel, except the desired unit, feet.

cancellation table

The ground distance is 12,000 feet.

USING THE MODIFIED ACREAGE GRID (TRANSPARENCY)

To use the acreage grid transparency, follow these steps:

acreage grid
 

Map Scales and Equivalents

Scale Inches per mile Acres per square inch Conversion factor that each dot equals
1:20,000 3.168 63.769 1.736 Acres
1:24,000 2.640 91.827 2.500 Acres
1:62,500 1.014 622.449 16.946 Acres
1:63,360 1.000 640.000 17.424 Acres

Table 5.2 Acreage Grid Overlay, Map Scales, and Equivalents.

  1. Place the acreage grid transparency over the area to be measured.
  2. Count dots inside the sketched area. Count every other dot when dots fall on the boundary line.
  3. Multiply the total number of dots by the conversion factor on the map scale to determine the total acreage. (See Table 5.2.)
  4. Example 3b - Using the information in Example 3a, find the ground distance in chains, miles, and inches.

    Step 1. Set up the cancellation table so all units will cancel, except the desired unit, chains.

    cancellation table

    12,000 feet = 182 chains
     

    Step 2. Set up the cancellation table so all units will cancel, except the desired unit, miles.
    cancellation table

    Step 3. Set up the cancellation table so all units will cancel, except the desired unit, inches.
    cancellation table
    12,000 feet = 182 chains = 2.3 miles = 144,000 inches

    Occasionally, a map may not provide a scale. The scale can be calculated by knowing the distance between two points on the map, and measuring the distance on the map. Also, if a map has section lines, the distance between section lines is typically 1 mile.

    Example 4 - The distance between point A and B is 6 inches on the map. The known ground distance is 3,600 feet. What is the scale in units of inches/foot?

    The map scale is 1:600 inches/foot.

    Example 5 - Use the map scale in example 6. The known ground distance between points B and C is 1/2 mile. How many inches is does this distance correspond to on the map?

    map scale = known distance / measured distance

    Rearrange terms by multiplying each side by the measured distance and dividing each side by the map
    scale.

    measured distance = known distance / map scale

    Step 1. Set up the cancellation table so all units will cancel, except the desired unit, feet.

    cancellation table

    Step 2. Use the map scale from Example 6 to find the map distance.

    measured distance = known distance
    map scale
    measured distance = 2,640 feet 1 inch = 4.4 inches
    600 feet

    On the ground one-half mile is the same as 4.4 inches on the map.









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NWCG Latest Announcements

NWCG Equipment Technology Committee Releases New Equipment Bulletins

Date: September 27, 2024
Contact: Equipment Technology Committee

The Equipment Technology Committee (ETC) has released three new Equipment Bulletins:

  • ETC-EB-24-003 Diesel exhaust fluid (DEF) in fuel containers.
  • ETC-EB-24-004 Two-compartment fuel and oil container (Dolmar) unavailable in the United States (US) and reminders for upkeeping current inventories.
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These bulletins remind field going personnel of important issues related to equipment for wildland firefighting efforts.

References:

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ETC-EB-24-003 Diesel exhaust fluid (DEF) in fuel containers

ETC-EB-24-004 Two-compartment fuel and oil container (Dolmar) unavailable in the United States (US) and reminders for upkeeping current inventories

ETC-EB-24-005 Personal Protective Equipment (PPE): Inspection, Care, and Maintenance

The Experiential Learning Subcommittee is looking for your feedback on Staff Rides

Date: September 20, 2024
Contact: Ashleigh D'Antonio and George Risko, Leadership Committee

The Experiential Learning Subcommittee needs to hear from the field about where the greatest need lies regarding staff rides and their accessibility.

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Fill out this short survey below to help us help you.

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Updated NWCG Single Resource Casual Hire Information, PMS 934

Date: September 19, 2024
Contact: Incident Business Committee

The Incident Business Committee has updated the NWCG Single Resource Casual Hire Information, PMS 934. This update expands the provisions for hiring emergency personnel.

References:

NWCG Single Resource Casual Hire Information, PMS 934

IBC Memorandum 24-03

NWCG 2024 Spring/Summer Highlights

Date: September 13, 2024

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Welcome to our latest highlights from the National Wildfire Coordinating Group, where we explore the latest updates, insights, and efforts that develop interoperable wildland fire operations among federal, state, local, Tribal, and territorial partners.

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NWCG Leadership Committee

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The Wildland Fire Leadership Development Program announced the Professional Reading Program’s 2024 list!

The years books include:

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In 2023, NWCG kicked off the Incident Performance and Training Modernization (IPTM) effort. A training system overhaul focused on developing a performance-based training system designed to shift training to on-the-job when appropriate.

Over the next five years, NWCG intends to analyze all positions within the NWCG Standards for Wildland Fire Position Qualifications, PMS 310-1. To date we are currently working on 30 incident positions, and planning for 20+ in calendar year 2025.

Subject Matter Experts from a variety of geographical areas and agencies recently completed the position analysis for 16 positions. From this analysis, Incident Positions Standards and a Next Generation Position Task Book will be developed for each position.

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NEXT GENERATION POSITION TASK BOOK

In April 2024, NWCG launched the new Next Generation Position Task Book (Next Gen PTB) which is a key component of the IPTM effort. This revised evaluation tool is designed to work in conjunction with the newly developed Incident Position Standards.

Major Next Gen PTB changes:

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