Create a buffer in decimal degrees

Buffers in Decimal Degrees: Taming the Geographic Wild West

Buffers are like those invisible force fields you see in sci-fi movies, but for the real world of maps and geography. In GIS (Geographic Information Systems), we use them all the time to mark out areas around things. Need to know what properties are within a mile of a proposed highway? Slap a buffer on it. Trying to figure out the impact zone of a potential oil spill? Buffers to the rescue! They’re super handy for all sorts of spatial analysis, from managing resources to making smart decisions based on location.

Now, you can create these buffers using different units of measurement, but things get a little tricky when you’re working with decimal degrees. Why? Because a degree isn’t always a degree, if you catch my drift. Let’s dive in.

Decoding Decimal Degrees

Think of decimal degrees (DD) as a way to pinpoint locations on a map using numbers. Latitude tells you how far north or south you are, ranging from -90 (South Pole) to +90 (North Pole). Longitude tells you how far east or west you are, going from -180 to +180. Easy enough, right?

The problem is, these degrees aren’t like meters or feet. They don’t translate to consistent distances across the globe. Imagine squeezing an orange peel flat – that’s kind of what happens when you project the Earth onto a 2D map. The distance covered by a degree of longitude shrinks as you head towards the poles, while latitude stays relatively consistent. So, a buffer that looks like a perfect circle in decimal degrees near the equator will be all wonky and distorted up north.

The Decimal Degree Dilemma: Why Buffers Go Bad

This inconsistency is the core challenge. If you create a buffer with a fixed decimal degree radius, say 0.1 degrees, it won’t represent the same real-world distance everywhere. That 0.1-degree buffer around a point in Ecuador will be way bigger than the same buffer around a point in Iceland.

Trust me, I learned this the hard way once when I was working on a project mapping potential habitats for migratory birds. I used a simple decimal degree buffer, and my results were completely off. The birds weren’t where my buffers said they should be! That’s when I realized I needed to get serious about understanding coordinate systems and projections.

Using decimal degrees directly as a unit of distance can lead to some seriously skewed results, especially if you’re dealing with large areas or comparing buffers in different parts of the world. It’s like trying to build a house with a rubber measuring tape – things are going to get weird fast.

Taming the Beast: Best Practices and Clever Tricks

So, what’s a GIS analyst to do? Don’t despair! There are ways to wrangle those decimal degree buffers and get them under control.

A Few Words of Wisdom

• Know Your Software: Every GIS program is a little different. Read the manual, watch some tutorials, and figure out how your software handles buffers.
• Data is King: Make sure your data is accurate and properly georeferenced. Garbage in, garbage out, as they say.
• Check Your Work: Always take a good look at your buffers to make sure they look right. Do they make sense in the real world? If something seems off, investigate!

The Final Verdict

Buffering in decimal degrees can be a bit of a wild ride. It’s like navigating with a compass that sometimes points in the wrong direction. But with the right knowledge and techniques, you can tame those buffers and get accurate, reliable results. While reprojecting is usually the best approach, understanding the ins and outs of decimal degree buffering is a valuable skill for any GIS professional. Now go forth and buffer responsibly!