However, throughout the United States, the elevations of various structures, landmarks, valleys, hills, and other features are set to change in relation to average sea level. Many of these locations will become shorter, with some areas in the Pacific Northwest expected to decrease by up to 5 feet and parts of Alaska by 6 1/2 feet, as stated by Juliana P. Blackwell, the director of the National Geodetic Survey. 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 relative to a specific reference point, and geodesists, who study the Earth's shape, size, gravitational field, and position in space over time, are updating this reference point, known as the vertical datum, from which height measurements are taken. It is an extremely challenging math and physics project that will take fifteen years to complete. According to Chris Rizos, president-elect of the International Union of Geodesy and Geophysics, the United States' efforts in this project are significant. The project, known as "height modernisation," is part of NOAA's broader initiative to accurately determine the country's position on Earth. The new National Spatial Reference System, which includes height, latitude, longitude, and time, is expected to be implemented in 2022 or 2023. This system will replace outdated reference systems from the 1980s that were less precise due to outdated technology. The discrepancies in elevation become more pronounced when traveling diagonally from the southeast to the northwest of the country. The only region in the United States projected to maintain its current elevation or experience a slight increase is the southern tip of Florida. According to Blackwell, there is a noticeable shift that results in all the inaccuracies in our vertical network being concentrated in the northwest. The concept of height has always been linked to pride. Blackwell mentioned that some residents of Colorado are concerned that a few of their mountain peaks may no longer meet the criteria for boasting rights under the revised elevation standards. “They are very proud of how high these things are, and I know that it’s going to be a bit of a disappointment if they start to be a little bit shorter than previously thought,” she stated. She mentioned that she is uncertain about the exact new measurements of Colorado’s peaks. In Beaumont, Texas, residents are dealing with the unsettling news that certain areas have sunk so much since the last height calculations that they now fall within the floodplain. Consequently, some property owners may need to obtain flood insurance to protect against potential losses, according to Daniel R Roman, chief geodesist at NOAA. “They were not happy to learn that the heights had changed,” he explained, “because when they conduct floodplain mapping, they assume, ‘Well, I’m at this height — it hasn’t changed.’” The US has been measuring its elevation since 1807, when President Thomas Jefferson established the Survey of the Coast, a precursor to the National Geodetic Survey, to map the waters and coasts of the Eastern Seaboard. The survey was the first scientific organization in the nation that was not military-related. Its goal was to improve the safety of shipping. As the country grew in the westward direction, so did the measurement process, with surveyors using the coast as a reference point for sea level to determine elevation. Metal bench marks were placed in the land by surveyors as they journeyed, detailing the height above sea level at each point, frequently on a mile-by-mile basis. Individuals wanting to measure the height of a structure or hill would do so in relation to the bench mark and ultimately, to sea level. Geodetic levelling, also known as the process, was meticulous and costly. The objective was to ensure that elevations were consistently measured nationwide over time, rather than each region having its own method. For instance, if engineers from different states were constructing a bridge spanning state boundaries, they needed to ensure that it would align in the center. By 1900, geodesy had advanced significantly. Geodesists no longer relied on a coastline as a substitute for sea level; instead, they created a model that accurately depicted sea level using tide readings. Since then, the height reference has been adjusted five times - in 1903, 1907, 1912, 1929, and 1988. The 1988 model is currently the standard in the US and Mexico. However, the 1988 version did not provide accurate information for California and parts of Texas and North Carolina due to significant movement in the crust caused by tectonic plate activity and extraction of oil, gas, and water from beneath the ground. To address this issue, geodesist David B Zilkoski, former director of the National Geodetic Survey, suggested utilizing technologies like GPS from the global navigational satellite system. GPS is very effective 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 the height above sea level. In the mid-1990s, the idea of using GPS to modernize height measurements became popular due to its affordability and simplicity. Satellites and GPS measure height in relation to a smoothed-out mathematical representation of the Earth's shape known as an ellipsoid. Imagine a basketball being compressed at the top and bottom. However, there was a significant complication. Geophysicist James L Davis from Columbia University's Lamont-Doherty Earth Observatory in New York pointed out that GPS technology is not well-equipped to account for gravity. This topographic research is being conducted in the Glacier Bay region of Alaska, as reported by The New York Times. A geodesist places importance on gravity, as it affects the measurement of height by determining the strength and direction of gravity's pull based on the density of the terrain below. Height is not just a measurement of distance above the ground, but is connected to gravity and the distribution of mass. Geodesists prefer to use the term "height" over "elevation" due to this relationship. Davis mentioned that in public lectures about gravity, a significant portion of the discussion is focused on changing the audience's perspective on the concept. As a result, relying solely on GPS for height measurements could be significantly inaccurate. If an engineer were to lay pipe using only GPS data without considering local variations in gravity, the water may not flow as intended. However, incorporating highly detailed measurements of the gravitational field into GPS height calculations is a challenging task. In 2007, the National Geodetic Survey initiated a major project called GRAV-D, aimed at redefining the American Vertical Datum by taking gravity readings into account. 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 across different locations, a model known as the geoid is shaped like a lumpy potato. All measurements of height will now consider this model. According to Blackwell of the National Geodetic Survey, once the new height system is implemented, people will discover unexpected uses for it. She referenced "The Jetsons," a futuristic animated show from the 1960s where characters traveled around in small spacecraft in their cities. The technology used in the show, such as the ability to quickly and accurately calculate heights and other positional coordinates, was previously unimaginable. Today, the importance of accurate navigation in three dimensions is increasing due to the prevalence of drones, self-driving cars, and remotely operated aerial systems. Despite advancements in calculating the shape of the Earth by geodesists, human activities such as global warming are altering the planet by melting glaciers and ice sheets, causing a shift in mass from land to ocean and ultimately changing sea levels and elevations. The change in mass is also impacting the planet's configuration. According to Davis from Columbia University, the mass on Earth's surface is causing it to change shape. Essentially, human activity through climate change is changing gravity on a global scale by altering the atmosphere and moving mass around, resulting in a significant amount of mass being affected. Scientists like Davis are currently working to better understand and calculate the impact of human activity on the Earth's geoid shape and rotation. They are focused on measuring changes in the Earth's shape, mass in glaciers, and predicting future events based on these factors. This research represents a shift from historical concerns about Earth's shape to more pressing questions about its changing state and potential future impacts.