Every other Friday, the Outside/In podcast team answers one listener question about the natural world. Editor's note: This episode was first published Oct. 1, 2021.
This week, Ian from Tamworth, New Hampshire asks:“New Hampshire is a pretty hilly mountainous state with a lot of wrinkles in the landscape, and I was wondering if you ironed out those wrinkles and flattened the whole state, how much bigger would it be by area?”
To help us answer this question, we spoke to Larry Garland, the cartographer for the Appalachian Mountain Club. Larry's computer has a popular mapping program called ArcGIS, which he said could give us an answer.
"But the data sets are just so huge. I mean, we're talking millions and millions and millions of pixels in the state of New Hampshire," said Larry.
Larry typically uses ArcGIS to calculate the mileage of a hiking trail: the combination of linear distance and mountainous elevation.
First, he hikes the trail with GPS equipment that gives him the distance traveled on the trail. Then, Larry takes this GPS data and plugs it into the ArcGIS software.
"I drape that onto a 3-D surface. And I use the software to calculate the surficial distance: the distance that that trail has as it lies on that terrain model," Larry said.
But until we asked him to, Larry had never tried using the same software to calculate the surficial distance of the entire state.
Still, it's the same basic process – instead of draping a line over a 3-D terrain model, Larry is draping an entire "cloth" over the state.
At least, that's how it ought to have worked in theory... the calculation was so big it crashed his computer. Twice.
So we decided to speak to Russell Congalton, professor of remote sensing and geographic information systems at the University of New Hampshire, to see if there's a way to answer this question without software.
Russell said that you could calculate the surficial area of New Hampshire by assembling hundreds of volunteers on the eastern border of New Hampshire with surveyors wheels and walking them across the state. And then by having them repeat the journey from south to north.
Russell said you could do essentially the same thing by buying a 3-D raised relief map of New Hampshire, draping string over it, and then measuring the string.
But before we could try this method, Larry Garland (the Appalachian Mountain Club map maker) reached back out. He had run the ArcGIS software again, and this time, he avoided crashing his computer by calculating each of New Hampshire's ten counties separately, and adding them together.
According to his calculations, New Hampshire is 133 square miles bigger when you iron out the wrinkles, which is just about 1.5 percent bigger.
This might not sound like a lot, but Larry gave a caveat with his answer: he ran this process at relatively low resolution.
Why does that matter? As one astute listener has suggested, it's related to something calledthe coastline paradox: the more detailed measurement, or higher resolution used, the bigger (but not necessarily more accurate) the final calculation will be.
So we've answered Ian's question as best as we can for now, but as many New Hampshire hikers have learned, the size of New Hampshire's topography has a way of shifting beneath your feet.
