A map in which the area of its units has been distorted to be proportional to the data the re is known as
Answers
Verbal Scale to RF
Verbal Scale to Graphic Scale
RF to Graphic Scale
RF to Verbal Scale
Graphic Scale to RF
3. Determining Scale from a Map or Photo
4. Determining Distance and Area from Map & Scale
A.Finding area measurement from map and scale
B. Measurement Scales
C. Accuracy, Precision, and Significant Digits
D. Classification, Simplification and Symbolization of Data
Source:
Map scale is the relationship between a unit of length on a map and the corresponding length on the ground. We will use concepts of map scale throughout the course, so it will pay you to study this section carefully.
1. Types of Map Scales
We can relate map and ground with three different types of scale.
Verbal scale expresses in words a relationship between a map distance and a ground distance. Usually it is along the lines of:
One inch represents 16 miles. Here it is implied that the one inch is on the map, and that one inch represents 16 miles on the ground. Verbal scales are commonly found on popular atlases and maps.
The second type of scale is a graphic scale, or bar scale. This shows directly on the map the corresponding ground distance.
For example:
The third type of scale is a representative fraction, or ratio scale. Compared to the first two, it is the most abstract, but also the most versatile. A representative fraction, or RF, shows the relationship between one of any unit on the map and one of the same unit on the ground. RFs may be shown as an actual fraction, for example 1/24,000, but are usually written with a colon, as in 1:24,000. In this example, one unit of any length (one mm, one cm, one inch, one foot, etc.) on the map represents 24,000 of those same units on the ground (24,000 mm, 24,000 cm, 24,000", 24,000', etc.). The RF is versatile because you are not tied to any specific units. You may work in any unit you choose, either metric, English, or other.
The RF is a called a fraction because it is just that--a fraction that shows how much the real world is reduced to fit on the map. A good comparison is often made with scale models of automobiles or aircraft. A 1/32-model of an auto is 1/32nd as large as the actual auto. In the same way, a 1:100,000-scale map is 1/100,000th as large as the ground area shown on the map.
A related idea is that of small scale versus large scale. Geographers use these terms differently than many people. A large scale map is where the RF is relatively large. A 1:1200 map is therefore larger scale than a 1:1,000,000 map. The 1:1,000,000 map would usually be called a small scale map. This is true even though the 1:1,000,000 map would show a much larger area than the 1:1200 map.
Here is a rule of thumb for size of scale by RF:
Size of Scale Representative Franction (RF)
Large Scale 1:25,000 or larger
Medium Scale 1:1,000,000 to 1:25,000
Small Scale 1:1,000,000 or smaller
Of course, what is small or large scale is relative. I noticed a surveying text (Brinker & Wolf, 1984) that classed anything smaller than 1:12,000 as small scale -- surveyors rarely work with anything smaller than this.
The large/small scale terminology can become confusing when talking about large versus small areas. If you are talking about a phenomenon that occurs across a large region, it is tempting to say it's a large-scale phenomenon (e.g., "the forest blight is a large-scale disease"). But since the map that would show this would be small-scale, it is better to use a different term to avoid confusion. My favorite is "broad-scale."
Many maps include two or even all three types of scales. USGS topographic maps have both bar scales and RFs.
2. Converting Between Scale Types
If you are given one type of scale, you should be able to derive or construct any of the other two. This takes some practice, and some problems are included in your lab exercises. Some examples are given below.
A vital step in doing any kind of conversion that involves differing units is to include the units in the problem itself. You can then cancel the units by multiplying or dividing. This way you avoid becoming confused about which conversion factors to use and how to use them.
Verbal Scale to RF
The key here is to write the verbal scale as a fraction, then convert so that both numerator and denominator have the same units, and the numerator has a 1.
(a) Convert verbal scale of "1" to 18 miles" to RF
or 1:1,140,000.
Notice that the resulting fraction is rounded so that the RF does not imply more accuracy than the original precision warranted.
(b) Convert verbal scale of "15 cm to 1 km" to RF
or 1:6700.
In many conversions you can save steps if you remember additional