A graphic scale, also known as a bar scale, is a way to represent map distances and their corresponding real-world distances using a visual line.
Understanding Graphic Scales
Instead of relying on numerical ratios, a graphic scale visually displays the relationship between distances on a map and the distances they represent on the ground. It achieves this by using a line marked with primary and secondary divisions.
Key Features of a Graphic Scale
- Visual Representation: A line is divided into segments, each representing a specific distance on the ground.
- Primary Divisions: These are the main markers on the scale, usually representing larger units of measurement (e.g., kilometers or miles).
- Secondary Divisions: These smaller divisions further refine the scale, enabling users to measure distances more precisely.
- Direct Measurement: You can directly measure distances on a map by comparing them to the graphic scale.
How to Use a Graphic Scale
- Locate the Scale: Find the graphic scale on your map, usually located in a corner.
- Measure on the Map: Use a ruler or your fingers to measure the distance you're interested in on the map.
- Compare with the Scale: Place the measurement against the graphic scale to determine the corresponding real-world distance.
Advantages of Graphic Scales
- Visual and Intuitive: Easier to understand than representative fractions.
- Remains Accurate: The scale remains accurate even if the map is resized, which is not the case with numerical scales.
- Practical: Useful for quickly measuring distances directly on the map.
Example:
Imagine a map with a graphic scale where each centimeter on the map represents 10 kilometers on the ground.
- If a line on the map measures 5 centimeters against the graphic scale, the real distance is 50 kilometers.
- A 2.5 centimeters measurement on the map means a 25 kilometer real-world distance.
Graphical Scale vs. Numerical Scale
Here is a table to illustrate the differences between Graphic and Numerical Scales:
| Feature | Graphic/Bar Scale | Numerical Scale |
|---|---|---|
| Representation | Visual line with divisions | Ratio or fraction (e.g., 1:25,000) |
| Accuracy with resizing | Remains accurate with map resizing. | Loses accuracy if the map is resized. |
| Ease of use | Intuitive for direct measurement | Requires calculation for determining real-world distances. |
| Purpose | Directly measures distances on the map with comparison to the line. | Indicates the mathematical relationship between map and ground. |
Conclusion
In summary, the graphic scale is a vital map element that provides a visual method for quickly and accurately determining real-world distances from a map. According to the provided reference, it "shows map distances and the corresponding ground distances using a line bar with primary and secondary divisions marked on it." It is especially handy because it remains valid even when the map is resized, which is often crucial for practical uses of maps.
