Lecture 4-Map Scale

how do you calculate a map scale?

1) Measure the distance between any two points on the map. This distance is the map distance (MD). 2) Determine the horizontal distance between these same two points on the ground. This distance is the ground distance (GD). 3) Use the representative fraction (RF) formula, and remember that RF must be expressed as:

Why is a large scale map referred to as large?

A large scale map is referred as "large" because the representative fraction (e.g. 1/25,000) is a larger fraction than one on a small scale map. A small scale map may have an RF of 1/250,000 to 1/7,500,000. Large scale maps will have a RF of 1:50,000 or greater

What is the difference between large scale and small scale maps?

A small scale map shows a large area with few details. A large scale map shows a small area with more details.

What units does the graphic scale include in the U.S.?

In the U.S., a graphic scale often includes both metric and imperial unit

what is a verbal scale? What are 3 example to represent one inch to two miles?

It uses words to describe the ratio between the map's scale and the real world. 1 inch to 2 miles 1 inch equals 2 miles 1 inch = 2 miles

What is map generalization?

Map generalization is the elimination of map detail as the scale decreases

What is a map scale

The mathematical relationship between distances on the map and their corresponding ground distances

How can a representative fraction be written? i.e. 1:50,000

The representative fraction can be written in the format as either 1/x or 1:x , where the numerator is always 1 and the denominator (x) represents distance on the ground. one centimeter on the map=50,000 centimeters on the ground

What is a scale bar?

a map element used to graphically represent the scale of a map. A scale bar is typically a line or a bar, segmented like a ruler, and marked in units proportional to the map's scale

What are two reasons to use a scale bar?

a) A scale bar is a straightforward, easy way to determine distances on a map. b) A scale bar changes size in proportion to the physical size of the map.

what kind of maps is the scale dynamic?

computer based or webbased

Why would RF and Verbal scale be ineffective?

if the map is reproduced by a method such as photocopying, which may change the size of the map. If the map size changes, the scale is lost: an inch measured on a smaller/enlarged map does not equal an inch on the original map. A graphic scale solves this problem because it doesn't change size if the map changes size; the map reader can use it with a ruler to determine distances on the map.

Does RF have units?

no

can you mix units in RF?

no

What kind of map is the scale fixed?

paper map

What are the three options for representing scale?

representative fraction (RF), verbal scale, and scale bar.

what scale does google maps use?

scale bar

What is Representative fraction?

the ratio between distance on the map and actual ground distance.