However, throughout the United States, the elevations of various structures, natural landmarks, and geographical features are expected to change in relation to average sea level. This shift will result in most areas becoming shorter in height. According to Juliana P. Blackwell, the director of the National Geodetic Survey, parts of the Pacific Northwest could see a decrease of up to 5 feet, while parts of Alaska may experience a 6 1/2 foot reduction. Seattle, for example, is projected to be 4.3 feet lower than its current elevation. This adjustment is due to the fact that height is relative to a specific reference point, and geodesists, who study the Earth's shape, size, and gravitational field, are updating this reference point, known as the vertical datum, to redefine how height is measured. The challenging task of recalibrating the US's position on the planet, known as "height modernisation," is nearing completion after fifteen years of work. This effort, led by the National Oceanic and Atmospheric Administration, aims to establish a more accurate spatial reference system encompassing height, latitude, longitude, and time. The new system is expected to be implemented in 2022 or 2023 and will replace outdated reference systems from the 1980s. According to Chris Rizos, this accomplishment is significant due to the scale of the operation and the advancements in technology that have made it possible. The discrepancies in elevation become more pronounced when traveling diagonally from the southeast to the northwest of the country. According to Blackwell, the only part of the US that is projected to maintain its current elevation or slightly increase is the southern tip of Florida. Blackwell noted that there seems to be a tilt in which all the inaccuracies in the vertical network are concentrated in the northwest. However, 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 a certain height standard under the updated system. She mentioned that people are proud of the height of certain things, and it would be disappointing if they were found to be shorter than previously believed. She is unsure of the new measurements of Colorado's peaks. In Beaumont, Texas, some areas have subsided so much that they are now in the floodplain, requiring landowners to insure themselves against flood losses. The US has been measuring its height since 1807. The survey was the first scientific organization in the country and was created to improve safety in shipping. As the nation expanded, so did the measuring process, with surveyors using the coast as a reference point for sea level. They placed metal bench marks in the land to indicate height above sea level, allowing others to measure buildings or hills relative to these points and indirectly to sea level. Geodetic levelling, also known as the process, was meticulous and costly. The goal was to ensure that heights were consistently measured throughout the entire country, rather than each region having its own method. For instance, if engineers from different states were constructing a bridge that crossed state borders, they needed to ensure that it would align perfectly in the center. By 1900, geodesy had advanced significantly. Instead of relying on a coastline to represent sea level, geodesists created a model that accurately depicted sea level using data from 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 was found to be lacking accurate information for California and parts of Texas and North Carolina due to significant movement of the crust in those areas from tectonic plate activity and extraction of oil, gas, and water from underground. Former director of the National Geodetic Survey David B Zilkoski suggested using global navigational satellite system technologies like GPS to address this issue. GPS is very accurate in determining your location in a two-dimensional setting, such as at a specific intersection. However, it can also provide your exact position in a three-dimensional environment, including altitude above sea level. In the mid-1990s, the idea of using GPS to update elevation became popular due to its affordability and simplicity. Satellites and GPS systems calculate height based on the Earth's mathematical shape known as an ellipsoid. Imagine a basketball that is flattened at the top and bottom. However, there is a major issue with GPS when it comes to understanding gravity, according to James L. Davis, a geophysicist at the Lamont-Doherty Earth Observatory of Columbia University in New York. This topographic work is being conducted in the Glacier Bay area of Alaska. Geodesists consider gravity to be important because height is determined by the direction in which gravity points, which can vary based on the density of the material beneath and near the surface. Therefore, height is not just a measure of distance above the ground, but is closely connected to gravity, which is influenced by the distribution of mass. Geodesists prefer to use the term "height" instead of "elevation" in their work. Davis mentioned that when giving public lectures on gravity, a significant portion of the talk is focused on getting the audience to think about it in a new way. Therefore, relying solely on GPS for height measurements can lead to significant inaccuracies, as it does not account for local variations in gravity. To address this issue, the National Geodetic Survey initiated the GRAV-D mission in 2007, aiming to incorporate detailed gravitational field measurements into GPS height calculations. This ambitious project will ultimately help geodesists create a more accurate model of average sea level worldwide, including on land. Due to the varying pull of gravity in different locations, a model known as the geoid is shaped like a lumpy potato. All measurements of height will now consider this model. Blackwell from the National Geodetic Survey mentioned that once the new height system is implemented, there will be unexpected uses for it. She referenced "The Jetsons," a futuristic animated show from the 1960s where characters traveled around their cities in small spacecraft. The technology needed to calculate heights and coordinates quickly and accurately was considered unimaginable back then. Today, the importance of accurate three-dimensional navigation is increasing due to the widespread use of drones, self-driving cars, and remotely operated aerial systems. Geodesists are improving their ability to calculate the shape of the Earth, but human activities such as warming the planet are altering it by melting glaciers and ice sheets. This shift in mass from land to ocean is raising sea levels and changing elevations referenced to sea level. The change in mass is also impacting the planet's structure. According to Davis from Columbia University, the mass on Earth's surface is exerting pressure and changing its shape. Essentially, human activity related to climate change is modifying gravity worldwide. By manipulating atmospheric chemicals, we are shifting mass on a large scale. Researchers like Davis are currently working to improve their calculations of the impact of human activity on the Earth's geoid shape and rotation. They are faced with the challenge of accurately predicting changes in the Earth's shape, mass distribution in glaciers, and their implications for the future. This ongoing research is seen as a race to accurately forecast what will happen in the coming years due to human influence.