Distance is measured on a scale by using the scale's representation to convert a measurement on a map or plan into the corresponding real-world distance.
Understanding scale is fundamental to interpreting maps and technical drawings. A scale establishes the relationship between the distance shown on the representation (like a map) and the actual distance on the ground or in reality. There are several ways scales are presented, but the core principle remains converting the measured distance using the scale factor.
Methods for Measuring Distance Using Scale
The process typically involves measuring the distance on the map and then using the scale to determine the actual distance.
1. Using a Ratio or Fractional Scale (e.g., 1:50,000)
This is a common method, particularly when using a scale that is expressed as a ratio.
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Step 1: Measure the Distance
Measure the distance between two points directly on the map or plan using a ruler. Note the unit of measurement (e.g., centimeters, inches). -
Step 2: Apply the Scale Ratio
The scale ratio (e.g., 1:50,000) means that 1 unit on the map represents 50,000 of the same units in reality. As highlighted in the reference, to find the real-world distance using a ratio scale: "To do this we times the distance we measure by the number on the right hand side of the ratio." So, if the scale is 1:50,000 and you measured 5 cm on the map, you multiply 5 cm by 50,000. -
Step 3: Convert Units
After multiplying, the result is in the same unit as your initial measurement (e.g., centimeters). "And then convert it to an acceptable unit." This means converting from centimeters to meters or kilometers (or inches to feet or miles) to get a practical real-world distance.- Example:
- Scale: 1:50,000
- Measured map distance: 5 cm
- Calculation: 5 cm * 50,000 = 250,000 cm
- Unit Conversion: 250,000 cm = 2,500 meters = 2.5 kilometers
- Example:
2. Using a Scale Bar (Graphic Scale)
A scale bar is a visual representation of the scale. It's a line or bar marked with distances corresponding to real-world distances.
- Step 1: Measure the Distance
Measure the distance between two points on the map using a ruler or a piece of paper. - Step 2: Align with the Scale Bar
Align the measured distance (on your ruler or paper) with the scale bar printed on the map. - Step 3: Read the Real Distance
Read the corresponding real-world distance directly from the scale bar. This method is often simpler as it visually performs the conversion for you.
Table: Types of Map Scales
| Scale Type | Description | Example | How it works |
|---|---|---|---|
| Ratio/Fractional | Expressed as a fraction or ratio, e.g., 1/100,000 or 1:100,000. No units specified (units are consistent). | 1:100,000 | 1 unit on map = 100,000 of same units in reality. |
| Verbal/Statement | Written statement relating map distance to real distance. | "1 cm equals 1 km" | Directly states the conversion ratio. |
| Graphic/Bar | A visual bar marked with real-world distances. | See example above | Use the bar to directly measure/convert visually. |
In summary, measuring distance on a scale means using the provided scale information – whether it's a ratio you multiply by or a bar you align with – to translate the measured distance on the map into the actual distance on the ground. The ratio method, as noted in the reference, involves multiplying the measured distance by the right-hand number of the ratio and converting units.
