However, throughout the United States, the elevations of various structures, landmarks, valleys, and hills are expected to change in relation to average sea level. According to Juliana P Blackwell, the director of the National Geodetic Survey, most of these features will decrease in height. In the Pacific Northwest, some areas may shrink by up to 5 feet, while parts of Alaska could see a decrease of 6 1/2 feet. Seattle, for example, is projected to be 4.3 feet lower than its current elevation. This shift is due to the fact that height is determined in comparison to a reference point, and geodesists are redefining this reference point, or vertical datum, which is used to calculate height. The completion of a complex math and physics task, expected to take fifteen years, is seen as a significant achievement by experts in the field. This effort, known as "height modernisation," is part of a larger initiative by the National Oceanic and Atmospheric Administration to accurately determine the position of the United States on the planet. The new National Spatial Reference System, which will include height, latitude, longitude, and time, is set to be implemented in late 2022 or 2023, replacing outdated reference systems from the 1980s. These older systems were based on calculations done before the widespread use of supercomputers and GPS technology. The inaccuracies in elevation become more pronounced when traveling diagonally across the country from the southeast to the northwest. The only part of the United States where elevation is predicted to remain steady or slightly increase is the southern tip of Florida. According to Blackwell, there is a noticeable incline that indicates errors in the vertical network are concentrated in the northwest. Elevation has always been linked to pride. Blackwell mentioned that some residents of Colorado are concerned that a few of their highest peaks may no longer meet the criteria for boasting rights under the updated elevation system. She stated that there is concern about the potential decrease in the height of certain landmarks in Colorado, and the exact measurements are still unknown. In Beaumont, Texas, residents are facing the challenge of certain areas sinking, causing them to now be in the floodplain. As a result, some landowners may need to obtain flood insurance. The US has been measuring its height since 1807, when Thomas Jefferson established the Survey of the Coast. The survey was the first civilian scientific organization in the nation, with the goal of improving safety in shipping. As the country expanded to the west, so did the surveying efforts, using the coast as a reference point for zero elevation. Surveyors placed metal bench marks in the land as they traveled, noting each point's height above sea level in detail. These bench marks were used by anyone needing to measure the height of a structure or geographical feature, allowing them to indirectly reference sea level. The process known as geodetic levelling was meticulous and costly. The goal was to ensure that heights were consistently measured in a standardized manner nationwide, rather than each region having its own methods. This was important for projects such as building bridges that crossed state lines, where engineers needed to ensure alignment. By 1900, advancements in geodesy had led to a more refined approach, with a model of sea level based on tide readings replacing the use of coastlines as a reference point. The height reference has been adjusted five times since 1903, with the 1988 model being the standard in the US and Mexico. However, this version was inaccurate for California and parts of Texas and North Carolina due to significant movements in the crust caused by tectonic plate activity and extraction of resources. Geodesist David B Zilkoski suggested using GPS technology to address this issue. GPS is very accurate in determining your location in a two-dimensional system, such as at a specific intersection. However, it can also provide your location in a three-dimensional world, including height above sea level. In the mid-1990s, the idea of using GPS to update height measurements became popular due to its affordability and simplicity. Satellites and GPS systems calculate height in relation to a smoothed-out mathematical representation of the Earth's shape known as an ellipsoid. Imagine a basketball that is compressed at the top and bottom. However, there was a significant issue. James L Davis, a geophysicist at Columbia University's Lamont-Doherty Earth Observatory in New York, pointed out that GPS technology has limitations when it comes to understanding gravity. This topographic research is being conducted in the Glacier Bay region of Alaska, as reported by The New York Times. Geodesists rely on gravity in their work, as height is determined by the direction and strength of gravity, which is influenced by the density of the terrain below and near it. This means that height is not just a measurement of distance above the ground, but is interconnected with gravity and mass distribution. Geodesists prefer to use the term "height" instead of "elevation" to reflect this relationship. Davis noted that when discussing gravity in public lectures, he often spends a significant portion of the talk encouraging people to reconsider their understanding of it. As a consequence, relying solely on GPS for height measurements could result in significant inaccuracies. Neglecting to consider local variations in gravity could lead to issues such as water not flowing properly through pipes. However, incorporating detailed measurements of the gravitational field into GPS data is a complex undertaking. In 2007, the National Geodetic Survey initiated a large-scale project called GRAV-D, aimed at redefining the American Vertical Datum by utilizing gravity measurements. Geodesists will use this data to create a model that accurately represents average sea level worldwide, including on land. Due to the varying pull of gravity, the geoid model looks like a lumpy potato and will be used as a reference for measuring heights. Once the new height system is implemented, it is expected that people will discover new and unexpected applications for it, according to Blackwell from the National Geodetic Survey. She referenced "The Jetsons," a 1960s animated sitcom depicting characters moving around cities in small spacecraft, to highlight how the technology to rapidly and accurately calculate heights and coordinates was previously unimaginable. In today's world, the importance of accurate navigation in three dimensions is increasing due to the widespread use of drones, self-driving cars, and remotely operated aerial systems. One expert believes that this technology will be adopted rapidly. While geodesists are improving their ability to calculate the shape of the Earth, human activities such as global warming are causing changes to the planet. The melting of glaciers and ice sheets is transferring their mass from land to the ocean, leading to rising sea levels and ultimately altering elevations referenced to sea level. The change in mass is impacting the planet's configuration as explained by Davis from Columbia University. The mass on Earth's surface is causing the planet to change shape. Essentially, human activity related to climate change is causing gravity to be altered globally. This is occurring through chemical changes in the atmosphere that result in the movement of mass, which is currently at a significant level. Davis and other scientists are currently working to improve the accuracy of calculating the impact of human activities on the Earth. They are particularly focused on understanding changes in the geoid shape and Earth's rotation. This research is crucial in predicting future events and is seen as a race to gather the necessary data.