; Map Scale
Documents
User Generated
Resources
Learning Center
Your Federal Quarterly Tax Payments are due April 15th

Map Scale

VIEWS: 4 PAGES: 14

• pg 1
```									Map Scale
Scale
• Ratio between distances on a map or globe,
and their actual ground distances.
Expressions of scale
1) Graphic scale (scale bar)
visual expression
line marked off in units
Good for making rough estimates of distance
Estimating Distance using Graphic Scale

• Mark off map
distance using
piece of paper
• Estimate distance
using the scale
bar.
Expressions of scale, cont.
2) Statement of scale
– Verbal expression
• Ex. One inch represents ten miles
– Easy to understand
Expressions of scale, cont.
3) representative fraction (RF)
– mathematical expression
– written as a ratio (sometimes as a fraction)
• ex. 1: 24,000        (same as 1/24,000)
• map distance unit : ground distance unit
• 1 : (some value)
– independent of units
– Good for more precise calculations of distance
– But you usually have to convert your answers
for them to be meaningful
• Ex. How far is 24,000 inches?
English System Conversions
• Inches to miles divide by 63,360
• Feet to miles: divide by 5,280
• Inches to feet: divide by 12

• Miles to inches: multiply by 63,360
• Miles to feet: multiply by 5,280
• Feet to inches: multiply by 12
Distance Calculations using Scale
1) Set up ratio
md      md
---- =   -----
gd       gd
• md is map distance; gd is ground distance
• one represents scale and the other is the
distance between two places.
Solving scale problems, cont.
• Rules
a) three values are known, insert these values and their
units of measure (if given)
b) units for numerators must be the same
c) units for denominators must be the same

2) Solve for the unknown value
– not necessarily the final answer
– Convert into appropriate unit of measure, if required
Example Scale Problems
1) The map distance between two towns is 10
inches on a map whose scale is 1:24,000.
How far apart are the towns?
md/gd = md/gd
1/24000 = 10”/x
1”/24000”=10”/x”
1*x = 24,000*10, or x = 240,000”
240,000”/63,360”per mi = 3.78 mi
2) Two towns are 15 miles apart and shown
four inches apart on a map.
a) what is the statement of scale?
4”/15mi = 1/x
4”/15mi = 1”/x mi
4x=15, so x = 3.75 mi
one inch represents 3 3/4 miles
b) what is the RF?
1”/3.75mi = 1/x
3.75 mi * 63,360 in/mi = 237,000 in
RF is 1:237,000
Relative Scale
• The larger the scale, the closer the map
comes to reality.
•
Scale      Mapped Area              RF denom
large      little, yet detailed     small
small      great, yet general       large
Relative Scale
Small Scale                       Large Scale

Example: 1:250,000 map vs. 1:24,000 map
Homework

```
To top