However, throughout the United States, the elevations of various structures and landscapes will soon be changing in relation to average sea level. Many will actually decrease in height, with parts of the Pacific Northwest and Alaska expected to shrink by up to 5 feet and 6 1/2 feet, respectively. According to Juliana P Blackwell, director of the National Geodetic Survey, Seattle will be 4.3 feet lower than its current elevation. This shift is due to geodesists redefining the reference point or vertical datum from which height is measured, as they calculate the Earth's shape, size, gravitational field, and orientation in space over time. The completion of a challenging math and physics task, expected to take fifteen years, is seen as a significant accomplishment by experts in the field. Chris Rizos, president-elect of the International Union of Geodesy and Geophysics, describes the United States' efforts in this area as important. This project, known as "height modernisation," is part of a larger initiative by the National Oceanic and Atmospheric Administration to more accurately determine the country's position on Earth. The new National Spatial Reference System, which includes height, latitude, longitude, and time, is scheduled to be implemented in late 2022 or 2023. This system will replace outdated reference systems from the 1980s that were not as precise due to limitations in technology at that time. The mistakes in elevation become more significant when traveling diagonally across the country from the southeast to the northwest. The only region in the US projected to maintain its current elevation or increase slightly is the southern tip of Florida. "There is a noticeable slant that indicates that all the mistakes in our vertical network are shifted towards the northwest," Blackwell explained. However, elevation has always been linked to pride. Some residents of Colorado are concerned that a few of their mountain peaks may drop below a certain threshold for bragging rights under the updated elevation system, according to Blackwell. “They are very proud of the height of these things, and it will be disappointing if they turn out to be shorter than previously believed,” she stated. She is uncertain about the exact new measurements of Colorado’s peaks. In Beaumont, Texas, residents are dealing with the news that certain areas have subsided so much that they now fall within the floodplain. As a result, some landowners may need flood insurance. Daniel R Roman, chief geodesist at NOAA, explained that people were surprised to learn that the heights had changed, as they had assumed they remained the same for floodplain mapping. The US has been measuring its height since 1807, when Thomas Jefferson established the Survey of the Coast, which later became the National Geodetic Survey. The survey was the first scientific agency in the nation, with the goal of increasing safety in shipping. As the country grew westward, so did the practice of measuring, with the coast serving 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, often mile by mile. Those wishing 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 laborious and costly. The purpose was to ensure that elevations were consistently measured nationwide over the years, rather than each region having its own method. For instance, if engineers from different states were constructing a bridge spanning state borders, they needed assurance it would align correctly. By 1900, geodesy had advanced. Rather than relying on a coastline as a reference for sea level, geodesists created a model of 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, but it lacked accurate information for California and parts of Texas and North Carolina. This is due to significant movement in the crust caused by tectonic plate activity and extraction of oil, gas, and water from underground. To address this issue, David B Zilkoski, a former director of the National Geodetic Survey, suggested using global navigational satellite system technologies like GPS, which were becoming more widely available at the time. GPS is very accurate in determining your location in a flat, two-dimensional space, such as at the intersection of Bank Street and Garden Avenue. However, it can also provide your location in a three-dimensional world, for example, Bank Street and Garden Avenue at an altitude of 40 feet above sea level. By the mid-1990s, the idea of using GPS to update elevation had become popular due to its affordability and simplicity. Satellites, and consequently global positioning systems, calculate elevation based on a simplified 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 does not have accurate information about gravity. This topographic research is being conducted in the Glacier Bay region of Alaska, as reported by The New York Times. Geodesists place importance on gravity because height is not just a measurement of distance above the ground, but also influenced by the strength and direction of gravity, which is affected by the density of the terrain below and near it. Therefore, geodesists refer to "height" instead of "elevation" to emphasize this connection. Davis mentioned that when discussing gravity in public lectures, a significant portion of the talk involves encouraging the audience to consider it from a different perspective. Therefore, relying solely on GPS for measuring height may result in significant inaccuracies. An engineer who neglects to consider local gravity variations when laying pipe with GPS may struggle to ensure proper water flow. Incorporating detailed gravitational field measurements into GPS height calculations is a complex undertaking. The National Geodetic Survey initiated the GRAV-D mission in 2007 to address this challenge. Geodesists will use gravity data to create a model that accurately reflects average sea level globally, including on land. Due to variations in gravity, the geoid model is uneven and likened to a lumpy potato. All heights will be measured with this model in mind. Once the new height system is established, unforeseen applications will arise, according to Blackwell of the National Geodetic Survey. She referenced "The Jetsons," a futuristic animated show from the 1960s where characters traveled in small spacecraft around their cities. The technology to quickly and accurately calculate heights and other coordinates was considered unimaginable back then. Today, accurate navigation in three dimensions is increasingly important due to the widespread use of drones, self-driving cars, and remotely operated aerial systems. Despite advances in calculating the shape of the Earth by geodesists, human activities such as global warming are altering the planet's shape 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 structure. According to Davis from Columbia University, the mass on Earth's surface is pushing down on the planet and changing its shape. Essentially, human-induced climate change is also modifying gravity worldwide. Davis explained that this is happening as a result of chemical alterations in the atmosphere that lead to the movement of mass. The current amount of mass being displaced is significant. Davis and other scientists are working hard to determine more precisely how to calculate the impact of human activity on the Earth, which is evident in the shape of the geoid and the Earth's rotation. They are striving to accurately measure changes in the Earth's shape and mass in glaciers in order to predict future events at specific locations in the coming years. This race to understand and predict the effects of the human footprint is a new challenge compared to centuries ago when the focus was on determining the Earth's shape.