How to Read and Interpret Scale Drawings

How to Read and Interpret Scale Drawings

Watch this video lesson to learn how scale drawings and legends are used on maps and blueprints. Learn skills that will serve you well when traveling and when looking at the blueprints of a car.

Scale Drawings

Believe it or not, math is responsible for so many things in our everyday lives. Without math, we wouldn't have things like maps or model drawings or cars, for example. I don't know about you, but I can't travel without a map. I would get lost somewhere and I wouldn't be able to find my way out. If I wanted to build a car, I would need a model drawing of the car so that I can know my measurements.

Now, you might be asking, what does all this have to do with math? Let me tell you. Both maps and model drawings are examples of scale drawings, accurately sized drawings that are either smaller or larger than what they represent. Both maps and model drawings are smaller version drawings. You can fit a map and a model drawing of a car in your pocket, but you can't fit a city or a whole car in your pocket.

These scale drawings are all about math. How so? Well, the author of the maps and model drawings needed math to figure out how much smaller to draw things. Everything needs to be smaller or larger by the same amount so that they are accurately sized smaller or larger versions of the original.

Legends

This is where the legend comes in. The legend tells us how much smaller or larger things in the drawing are. For example, on a map we might see a legend that tells us that 1 inch on the map equals 50 miles in real life. We might see it written out in math form such as 1 inch: 50 miles, and we might see it in the form of a ruler with inch marks that read 50 miles, 100 miles, and so on instead of 1 inch, 2 inches, and so on.

We might see the same on a model drawing, but with different numbers of course. A model drawing might read 1 inch: 12 inches. So, 1 inch on the drawing would equal 12 inches in real life. Why don't we look at a couple of real life examples?

Reading a Map

Look at this map:

Map of San Francisco Bay Area

It is a map of the San Francisco Bay Area. There are a few places here that I really want to visit. Starting in San Francisco, I want to make my way down to Santa Cruz and then to Sacramento. How can I make use of this map to find out how far away San Francisco is from Santa Cruz and Santa Cruz from Sacramento?

I see my legend that tells me how much smaller the map is. It tells me that for every bar at that distance, it is 50 miles in real life. How can I use this to help me find my information?

Well, I can take the bar and use it to measure the distance from San Francisco to Santa Cruz by seeing how many bars it takes. It looks like it takes a bit more than one bar to go from San Francisco to Santa Cruz. So, that tells me that the distance is about 70 miles from San Francisco to Santa Cruz. Doing the same for the distance between Santa Cruz and Sacramento, I see that it takes about 3 bars, so the distance is about 150 miles.

Reading a Model Drawing

Now, let's take a look at a model drawing of a car:

A car

These model drawings are also called blueprints. Yes, you can use these drawings to build their life-size versions. You can see that this model drawing shows the real world measurements of the car. I can use this information to build the car pictured here to its proper size. I see that the measurement between the front tires is 1,345 millimeters. This is a rather small car. I can look at the other measurements that are listed to continue building the car.

Lesson Summary

Now, it's time to review what we've learned. We've learned that a scale drawing is an accurately sized drawing that is either smaller or larger than real life. The legend tells us how much smaller or larger things in the drawing are. Examples of scale drawings and legends can be found in real world maps and model drawings of things such as cars.

You will find on the drawing itself a legend that tells you how big something is supposed to be in the real world. You can refer to this legend to find the distance between places on a map and to measure the size of objects in a drawing. A legend can say something like 1 inch: 12 inches, meaning that every inch in the drawing equals 12 inches in real life. The legend can also be a bar that looks like a ruler, which shows the distance in real life of that bar. We use this legend to read and interpret our scale drawings.