Mapping‎ > ‎

Map and Field Measurements

Map Scale & Map Distance

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. 

Scale

Rep.

fraction

Map (in/mi)

Map (in/ch)

Feet per map inch

1:253,440

253.44

0.25

0.0031

21120

1:126,720

126.72

0.50

0.0063

10560

1:63,360

63.36

1

0.0125

5280

1:62,500

62.5

1.01

0.0127

5188

1:31,680

31.68

2

0.025

2640

1:24,000

24

2.64

0.033

2000

1:21,120

21.12

3

0.0375

1760

1:15,840

15.84

4

0.05

1320

1:7,920

7.92

8

0.1

660

Firefighter Math Map Scale; Firefighter Math Spread/Map Distance

Slope Estimation

Slope (Degrees)

Slope (Percent)

10º

17.6 %

20º

36.4 %

30º

57.7 %

40º

83.9 %

45º

100 %

50º

119.2 %

60º

173.2 %

70º

274.7 %

80º

567.1 %

90º

Standard LANDFIRE slope themes are represented in units of degrees (°).  Many locally produced landscapes over the year’s stored slopes in percent (%).  It is much easier to estimate slope in %, estimating the elevation change and the horizontal distance and calculating the ratio.  BehavePlus, and BEHAVE tools before that, default to slope input in %.

Firefighter Math Slope Percent and Slope Angle

To convert from slope in degrees (°) to slope in percent (%), a scientific calculator is needed. 

1. Enter the slope in degrees
2. Press the Tangent button
3. Multiply the result by 100 to get slope in %


Unit Conversions

Online and downloadable apps are available from Apple (OSX & IOS), Google Play (Android), and MS Windows for making unit conversions for distance, temperature, area, volume, weight, time, energy and other items. 

Metric Unit

Multiply by

English Unit

Multiply by

Metric Unit

Meters/min

3.28084

Ft/min

0.3048

Meters/min

Meters/min

2.982582

Ch/hr

0.33528

Meters/min

Meters/min

0.03728

Miles/hr

26.8224

Meters/min

Kg/m3

4.460897

Tons/ac

0.22417

Kg/m3

Kg/m3

0.062

lb/ft3

16.129

Kg/m3

Tonnes/ha

0.44609

Tons/ac

2.2417

Tonnes/ha

Kw/m

0.28909

BTU/ft/sec

3.4592

Kw/m

Meters

0.049709

Chains

20.117

Meters

Meters

0.3048

Feet

3.28084

Meters

Millimeters

0.0393701

Inches

25.4

Millimeters

kilometers

0.62137

miles

1.6093

kilometers

hectares

2.4711

acres

0.40469

hectares

Firefighter Math Conversions reference provides several tables and conversion factors for the user.

Average Latitude for Each State

Alabama

33

Louisiana

31

North Dakota

47

Alaska

65

Maine

45

Ohio

40

Arizona

35

Maryland

39

Oklahoma

35

Arkansas

35

Massachusetts

42

Oregon

44

California

38

Michigan

43

Pennsylvania

41

Colorado

39

Minnesota

46

Rhode Island

41

Connecticut

41

Mississippi

32

South Carolina

34

Delaware

39

Missouri

39

South Dakota

44

Florida

28

Montana

47

Tennessee

36

Georgia

33

Nebraska

41

Texas

32

Hawaii

21

Nevada

39

Utah

39

Idaho

45

New Hampshire

44

Vermont

44

Illinois

40

New Jersey

40

Virginia

37

Indiana

40

New Mexico

34

Washington

47

Iowa

42

New York

43

West Virginia

38

Kansas

39

North Carolina

35

Wisconsin

44

Kentucky

37

Wyoming

43

Declination

Global Reference: https://maps.ngdc.noaa.gov/viewers/historical_declination/

Calculator: https://www.ngdc.noaa.gov/geomag-web/#declination


US/UK World Magnetic Model - Epoch 2015.0 Main Field Declination (D) 

(East Declination in Red, West in Blue; subtract from true compass reading)

Declination Map