The tallest mountain in the U.K. has just been re-measured for the first time since 1949 using modern GPS technology, revealing that it is in fact marginally higher than previously thought.

Located in the Scottish Highlands, Ben Nevis has been portrayed on maps for the past 66 years as standing at 1,344 meters (4,409 feet) above sea level. However, according to the latest, more precise measurement using GPS (Global Positioning System), the mountain’s peak is in fact 1,344.527 meters high (4,411 feet 2 inches), and as such can be rounded up to 1,345 meters.

Ben Nevis is thought to be growing at a rate of around a millimeter per year, which means that at the time of the last measurement its height would have been low enough to have been rounded down rather than up. However, given the equipment with which recordings were made at that time, it is unlikely that researchers would have known the height of the mountain with enough precision to provide a reading to the nearest centimeter.

GPS is a navigation system that uses information received from a number of satellites in order to determine the location of an object on Earth with extreme precision. Speaking to BBC News, Mark Greaves, who formed part of the team that conducted the new reading, explained that “the GPS in your phone can be out by several meters… because there are errors in the signals coming down from the satellites.”

To filter out these errors, the team compared the data received on the mountain with other readings from “highly accurate, permanent GPS stations nearby.” In doing so, they were able to obtain a measurement with a degree of precision in the order of millimeters.