The White Mountains are a legendary playground for hikers. For those who like an extra challenge there’s the New Hampshire 48 – the 48 mountains in the state with elevations over 4,000 feet.

But a new survey is calling almost all our summit elevations into question - and signal a possible change to the famous list of New Hampshire’s 4000 footers.

Listen to the radio version of the story here.

Over the past few years the United States Geological Survey has been flying aircraft over the state to more accurately assess New Hampshire’s topography using a laser based technology known as LIDAR.

AMC cartographer Larry Garland says significant changes are coming to our mountain maps. “Most of the summit elevations that I've looked at vary from our so-called traditional or past elevations by maybe 10 feet or so,” Garland says. “There's one or two outliers you know peaks that were off by 20 or 30 feet.”

And while Garland says Mount Washington’s summit elevation won’t be changing, there may be some revision coming to the official New Hampshire list of 4000 footers.

Mountains could be added – and some, like Waterville Valley’s Mount Tecumseh, now listed at 4003 feet, may be removed. “The LIDAR data indicates that the summit elevation of Tecumseh is 3,995. But whether or not the AMC 4000 Footer Club will decide to keep it on or take it off the list is going to be their call,” Garland says. “I'm inclined to think because of the way they've handled these things in the past that they may very well actually revise the list.”

AMC Guidebook author Steve Smith is a member of that 4000 Footer Committee. “You know it's just a matter of whether we want to, you know, go with the cold hard facts of the surveyors or go with tradition,” Smith says. “There is precedent for keeping lower peaks on the list in other areas of the Northeast. The Adirondack 46ers - their original list was done in 1920 of 46 peaks and then later surveys showed that four of them were below 4000 but they decided to adhere to tradition and keep them on the list. I will confess that I'm leaning towards keeping Tecumseh on the list but you know everyone will have their say and we’ll take a vote.”

Smith says that Mount Tecumseh isn’t the only mountain on the chopping block. “This could affect some of the peaks that are just barely over 4000 feet like Mt. Isolation and Mt Waumbek which are both just barely over 4000 feet,” he says.

Adding some intrigue to all this - having a summit elevation of 4,000 feet isn’t the only criteria the committee uses. To make the list, a mountain peak must also rise at least 200 feet higher than its neighboring “col” - the low ridge connecting it to the next mountain.

Potentially good news for Mount Guyot which at 4580 feet has always had the elevation, but was believed to lack the needed 200 foot rise. “We know from the data that the col towards South Twin is now 220 feet deep by the LIDAR,” Smith says, “but I don't think the data on the other side has been released yet. So that will be the determining factor on that one.”

One thing Smith can say for sure - this new data will be included in the next AMC guidebook. “Apparently almost all the elevations are going to change,” Smith says. “You know the numbers are going to change - maybe by only two feet or maybe I think I've seen a couple that have changed by as much as 30 or 40 feet. So we'll certainly be using those in the next edition of the guidebook which would be 2022 presumably. And Larry will be creating all new maps for that edition.”

As for Larry Garland, he says he’ll be climbing Tecumseh whether it’s on the list or not. “Tecumseh is not lost. It's still there,” Garland says, laughing. “And you can still climb it - but it is sort of a heads up that change is coming.”

The 4000 Footer Committee will meet later this spring when Garland’s assessment is complete.