Regardless on where you stand with the DAPL situation (I’m anti-DAPL but that’s a different conversation), pipelines and their safety are on people’s minds. There are certainly many ways to analyze these safety concerns, and one great way is through maps. However, like any other news source, maps can lie, and when they lie, people can misunderstand the situation and be misled. As a lover of cartography and the benefits it offers the world, seeing a map that is poorly constructed and potentially lying widely shared sets me on fire. Maps are so incredibly useful, and I love when people turn to maps to understand their world a bit better, but if those maps can’t hold up to critical analysis, they cause people to lose trust in the medium, but also wonder if maps are a worthy pursuit at all.
I recently dealt with this situation with this map on the dangers of pipelines in the U.S. It’s a video lapse that displays all pipeline-related deaths, injuries, oil spills, and a category referred to merely as “Natural gas” in the U.S. since 1986 to present day. There are many, many issues with it, and while I would love to point them out in detail, I want to point to it as an example of what a person unfamiliar with map basics should look for to ensure they’re reading a map worthy of their time:
1. Is it projected?
I’ll admit – unprojected maps are one of my biggest pet peeves in the whole wide world of mapping. This points to my background as a student who took a course in the principles of GIS, but the fact is, when a map is unprojected, there’s a good chance its wrong. Not all maps need to be projected of course, but standalone maps such as the one above does. The U.S. is an easy map to see if it’s projected or not – the states first off look weird, but most U.S. map projections curve the U.S., which is most noticeable in the North, where when unprojected, Washington, Idaho, Montana, North Dakota, and Minnesota all appear to have incredibly straight edges. A map projection is an attempt by the cartographer to display an area as closely to the way it would look on the globe. It is an attempt in accuracy of where things are. When a map is unprojected, nothing on it is as close to where it should be as where it would be when projected. Here’s an example of what a projected U.S. map should look like versus an unprojected map:
2. Is the data source clearly available?
Sources, sources, sources! The good news about GIS information is that it’s harder (or at least not as worth it) to come up with fake map information, but the issue is that maps lie, and a lot of that comes from the way the cartographer chooses to display the information. Data can be manipulated in so many different ways, which is why its always good to see an attribution to the data sources on the map – you can confirm that the data comes from a reputable source, which is thankfully the case with this map, as it comes from the U.S. Department of Transportation.
3. Is the legend telling you everything about what’s going on with the map?
In the case of this map, there isn’t a ton of clarity – one of the symbols is defined as “Hazardous liquids (mostly oil)” which doesn’t actually tell you when those liquids are. What do they mean by “mostly”? How do they measure what is “mostly”? By half? By 80%? It would make more sense for the sake of clarity to have a list of what those liquids can be, or at least what percentage of the liquids are oil. Also, note that it also says the points for that category are scaled by spill size, but do not show you what the scale is or what they mean by size – is it measured in the amount of liquid spilled or the area covered?
The point is, your legend is supposed to clarify what appears on the map. It should be simple and straightforward, and answer any basic questions you may have about the information on the map. That’s not quite what happens here.
4. Can you tell who commissioned the map?
Cartographers are often asked to make maps for people, businesses, and other entities. When this happens, it’s important to make it clear who asked for the map so that way any interests can be made known to the reader. It’s fine for an environmental group to request a map, but it is always worth knowing that they’re the ones who requested it so the reader can see for themselves why a cartographer might have left out or emphasized something on a map.
Those are the basics! I also think it’s important for a map to be visually appealing, but that’s just me and my cartographic eye. If you have any opinions or questions about evaluating maps for validity, please comment below!