The primary advantage of a bar scale on a map is that it remains accurate even if the map is resized.
When a map is resized (enlarged or reduced), a bar scale, also known as a graphic scale, changes proportionally with the map's features. This ensures that the ratio between distances on the map and corresponding distances on the ground remains correct. This contrasts with other map scale representations, such as representative fractions (e.g., 1:24,000) or verbal scales (e.g., "1 inch equals 1 mile"), which become inaccurate if the map is resized without updating the stated scale.
Here's a breakdown of the advantages:
- Resizing Accuracy: As mentioned, a bar scale adjusts automatically with the map's dimensions. This is crucial when maps are copied, scanned, or displayed digitally, where size variations are common.
- Ease of Use: Bar scales are visually intuitive and easy to use. Users can quickly estimate distances by comparing the bar scale's segments to distances on the map. No mathematical conversions are needed.
- Versatility: They work well with various map projections and can be used on maps of any size.
- Durability: Unlike written scale representations that can be easily obscured or erased, a bar scale is an integral part of the map graphic.
Example:
Imagine a map with a representative fraction scale of 1:100,000 is photocopied and enlarged by 20%. The representative fraction is now incorrect. However, if the same map has a bar scale, that bar scale will also enlarge by 20%, maintaining its accuracy. A user can still use the bar scale to accurately measure distances on the enlarged map.
In summary, the bar scale's ability to adapt proportionally to changes in map size makes it a reliable and practical tool for determining distances on maps, especially when dealing with resized or reproduced maps.
