Hello human geographers, we are back at it again this evening. Tonight we are going to be talking about a specific aspect of cartography and that is scale. Here's the definition. Scale is the representation of a real world phenomenon at a certain level of reduction or generalization, generally the relationship between the portion of earth being studied and the earth. as a whole.
Scale is the extent, the scope, of a geographic area that is under investigation. And this definition introduces us to the idea that there are different types of scale. So let's take a look at them. As we just mentioned, there are different types of scale. On the left, we have cartographic scale.
This is the most challenging of the bunch and the one that you're probably least familiar with. Cartographic scale is the degree to which something has been reduced on a map compared to the same space or feature on the Earth. In short, cartographic scale is the depicted size of a feature on a map versus real life. And there are three ways to communicate cartographic scale. A verbal or written statement that you see on the bottom.
A representative fraction, which is abbreviated RF scale. And you see that on the top. Or a graphic or visual scale that you see in the middle.
The other side of this slide you're probably more familiar with. Phenomenon scale. is the scale we use to describe at what level something is happening.
Perhaps the best example is something we're all quite familiar with. COVID-19 was a global pandemic. That's the phenomenon scale. It's happening globally.
And the four most common types of phenomenon scale are global, regional, national, and local. Global, as we said, is when something occurs more uniformly across large geographic areas. As we said with COVID, regional can refer to continents like North America, or it could refer to subsections of continents like South Asia. But it's smaller than global, and it's larger than just a single country. Because national scale refers to a phenomenon that's happening within a specific country.
And then finally, local means within a country. It could be a specific state or province or even a smaller area like a county, city, or neighborhood. Phenomenon scale may use terms like large-scale or macro to refer to global or it could use small-scale or micro to refer to local. But you have to be careful with that, as you're going to see.
So let's spend a little more time with cartographic scale. Cartographic scale allows us to measure absolute distance. This impacts the analysis of the map and therefore its purpose. One way to describe cartographic scale is a written statement.
In this example, one inch on the map represents 10 miles on the surface of the Earth. Another way is the graphic scale, which is a visual representation of space. So this amount of space on the map represents 10 miles on the surface of the Earth. Probably the most challenging of these three is the representative fraction. When we talk about our F scale, the number in the numerator is the same unit of measurement as the number in the denominator.
So, in the example on the screen, one unit on the map equals 633,600 of the same unit on the Earth's surface. But what's cool is that it doesn't matter what unit we use. One inch on the map equals 633,600.
inches on the Earth, one meter on the map equals 633,600 meters on the Earth. but you can't change units. So just to clarify, you can change units with word statements, like saying 1 inch equals 10 miles, but not with representative fractions. With cartographic scale, you will see the terms large scale and small scale used to refer to the level of detail that is visible on the map. So a very small area.
that provides lots of detail would be a large scale map. And that's kind of the opposite from what we just said with phenomenon scale, where a large scale would mean a large area. So from here on out, to avoid confusion, when we say large scale, we're going to be talking about cartographic scale.
When we need to reference a phenomenon that's happening over a large area, We'll say it's happening globally or it's happening at the macro scale. So let's see if we can come up with a mnemonic device to help us remember this. A mnemonic device is anything that we could use to help us remember something, a little trick. For me, I remember this by saying large scale, lots of detail.
Large scale, lots of detail, kind of rhymes, right? If I remember that, I can work out the rest of my flow chart. A large scale.
Part of graphic scale means your map will have lots of detail. It has lots of detail because it's a small area. A smaller area is going to have a smaller number in the representative fraction.
Now, this is when it comes full circle. If it's a smaller RF number, that's a larger fraction. Think of pizza. One pizza has four slices. And one has 12 slices.
The smaller number, 4, means each slice or each fraction is a larger part of the whole pizza. So a larger fraction is found with larger cartographic scales. And it doesn't remember, it doesn't matter how you remember this. Maybe math is like a second language to you and you just need to remember large scale, large fraction, you're good.
That's awesome. As long as you can work through this, but I would definitely write down this flowchart or some other mnemonic device into your notes because I can just about guarantee you will see an AP exam question about this. And if this still doesn't make sense, please bring those questions to class.
The final type of scale tonight is certainly the most important. Just like you will need to know the type of projection and the type of thematic map, I will almost always be asking at what scale are we analyzing this? This refers to the scale at which the data is grouped together or aggregated. Is the data grouped by country or in the U.S. by states, which are our subnational units? Is the data grouped by counties or census tracts?
When we ask what the scale of analysis is, you need to look at how much space is being covered. If it's just differences between neighborhoods, then it's probably census tract data. If it's differences between countries, that data is probably grouped at the national scale. But how does a cartographer decide at what scale they should conduct their analysis?
It depends on the story they're telling. Let's use a hypothetical example. Let's say you work for a national retail chain and you're trying to decide where to build a new store. Data at the national scale won't really be helpful. Instead, if you zoomed in to the zip code scale, that might give you a better idea where you could build a new store.
You could find the areas with potential customers who aren't having their needs met. It just depends on the story. The reality is that what happens at one scale affects processes at other scales.
So if we only use one dataset at a single scale, it may obscure the actual spatial pattern. So by examining the same variable at different scales, we can gain a greater understanding of our world. For example, This graduated circle map of followers of Buddhism tells us that most Buddhists are clustered in Asia. But we don't want to assume that it's uniformly distributed, uniformly dispersed across all of Asia and the Pacific, so we change the scale. By looking at data aggregated or grouped at the national scale, we can see from this choropleth map that countries like Thailand and Cambodia have more than 90% of their population that identifies as Buddhist.
But what about China? Only 18% of China identifies as Buddhist. But is that uniform throughout the country? Well, no.
When we change to a sub-national scale, or provincial scale as it's called for China, we see that the Buddhist population is especially prominent in just a few provinces. notably Tibet, where the home of the Dalai Lama was located, while the rest of China has a minimal Buddhist population. Now, while it was easy for me to include various maps of data at different scales of analysis, the reality is that you may not be able to change the scale. Instead, you will need to think like a geographer and ask yourself what would happen if...
I changed the scale. How would the story change? We have to be critical thinkers. We have to ask questions.
We have to think like geographers. Anytime you see a map, start asking questions. And if you can do that, you will be very successful. And that's where we will end tonight.
Have a wonderful evening and I'll see you back in class.