Over a billion measurements collected in fifteen years describe planet Earth, an essential reference for cartography, GPS and climate research

If the Earth were perfectly homogeneous, its gravitational field would have a regular distribution and the average ocean level would coincide with an almost perfectly ellipsoidal surface. The reality is very different. The density of rocks, the presence of large mountain ranges, the conformation of the ocean floor, and even the movements of the mantle locally modify the intensity of gravity, generating an irregular surface that geodesists call geoidIt is precisely this invisible form that a new visualization of the NASA Scientific Visualization Studio finally makes it understandable even to a non-specialist audience.

The three-dimensional model published in July 2026 does not therefore represent the physical surface of the planet, but rather a equipotential surface of the Earth's gravitational fieldIn other words, it describes the shape an ideal ocean would take, free of tides, winds, currents, and weather variations, subject only to the action of gravity. It is a fundamental surface for defining the very concept of sea level and constitutes one of the most important references in modern geodesy.

To make perceptible variations that in reality are of the order of a few tens of meters distributed across the entire planet, the authors of the visualization have amplified the model vertically by a factor equal to 10.000The effect is that of an Earth resembling an irregular potato, an image that has been circulating on social networks for years but is often mistakenly interpreted as the planet's true shape. In reality, the Earth's radius remains close to 6.371 kilometers, while the undulations of the geoid only oscillate between about +85 meters, recorded in the vicinity of Iceland, and −106 meters, in the southern Indian area.

This representation is primarily a scientific tool. Understanding how the gravitational field varies means improving satellite positioning, calculating elevations more precisely, studying ocean circulation, and monitoring the movements of large masses of water or ice due to climate change.

Fifteen years of observations collected by nineteen satellites

The new reconstruction arises from the global gravitational model GOCO06s, developed within the framework of the international project Gravity Observation CombinationThe dataset integrates over a billion observations collected over a period of approximately fifteen years da nineteen satellite missions, combining measurements from different instruments and different orbits to obtain one of the most accurate descriptions of the Earth's gravitational field available today.

Among the most important missions are: GRACE (“Gravity Recovery and Climate Experiment”) by NASA e Goce (Gravity field and steady-state Ocean Circulation Explorer) of the European Space Agency. The two initiatives adopted complementary approaches. GOCE measured local gravitational accelerations with extreme precision, while GRACE observed variations in the gravitational field over time by detecting microscopic changes in the mutual distance of two satellites in the same orbit.

This principle allows for the detection of extremely small variations in mass. When one of the two probes flies over a slightly more massive region, it is accelerated imperceptibly relative to the other. By continuously measuring this distance with extremely precise instruments, it becomes possible to reconstruct the distribution of Earth's mass and follow its evolution over time. It is thanks to this methodology that it is now possible to quantify the mass loss of large ice sheets, monitor the depletion of aquifers, and observe the effects of large earthquakes on the planet's mass distribution.

The contribution of satellite missions does not completely replace ground-based measurements, but it allows for standardized observation of the entire globe, including vast ocean areas and remote regions where traditional gravimetric campaigns would be extremely expensive or impossible to carry out.

From the geoid to GPS navigation systems for everyone's future

The availability of an increasingly accurate gravitational model produces effects that go far beyond academic research. All modern satellite positioning systems, from GPS American to Galileo, up to the other global constellations, determine the position with respect to a mathematical ellipsoid, a regular surface chosen as a geometric reference. The dimensions that are of interest to engineers, cartographers, geologists and civil protection, however, must be referred to the mean sea level, represented precisely by the geoid.

The difference between these two surfaces can reach tens of meters depending on the region of the planet. Without a reliable gravity model, a satellite receiver would be able to precisely determine its position in space, but it would not be able to automatically convert that measurement into the altitude actually used in topographic maps, civil infrastructure, or engineering works.

The same principle is fundamental to the construction of bridges, tunnels, dams, high-speed rail lines, and geological monitoring networks. Even seemingly negligible differences can accumulate over large distances, making increasingly precise knowledge of the distribution of the Earth's gravitational field indispensable.

A key to observing climate and the movements of the land mass

Gravitational measurements are currently one of the most effective tools for observing phenomena that cannot be directly detected through optical images. When a large ice sheet loses mass, when an aquifer becomes depleted, or when huge quantities of water are transferred from the oceans to the continents, the distribution of Earth's gravity also changes. Dedicated satellites are able to record these variations with extremely high sensitivity.

For this reason the models derived from the missions GRACE and subsequent observation campaigns have become an essential component of contemporary climatology. They allow us to estimate the mass balance of the Greenland,Antartide, of large mountain glaciers and numerous river basins, providing data independent of observations made using radar, laser or multispectral images.

Oceanography also benefits from this information. Ocean currents are not determined solely by wind and temperature, but follow extremely small differences in gravitational potential. Knowing the geoid therefore allows us to distinguish the theoretical mean ocean level from the variations actually produced by marine dynamics, improving the interpretation of altimetric measurements collected by satellites.

The same logic is applied to the study of deformations in the Earth's crust caused by large earthquakes or long-lasting geological processes. Although often minimal, these changes alter the distribution of mass and leave measurable traces in the gravitational field.

A spectacular representation that tells an invisible reality

The visualization created by the NASA Scientific Visualization Studio It also has an important educational value. The irregular appearance of the geoid can in fact lead one to believe that it represents the true physical shape of the planet, when in fact it only describes the geometry of its gravitational field. The vertical exaggeration of a factor 10.000 It serves precisely to make observable differences that, in reality, would be practically imperceptible on an Earth with a diameter greater than twelve thousand kilometers.

This distinction is also fundamental from a scientific perspective. The visible Earth's surface is determined by topography, while the geoid depends on the distribution of internal masses. The two geometries can only partially coincide: a mountain range generally produces a positive gravitational anomaly, but the relationship is never perfectly direct because of different rock densities, crustal thicknesses, deep mantle structures, and geological dynamics that have developed over millions of years.

The new model thus represents a benchmark for numerous research fields. From geodesy to satellite navigation, from climatology to oceanography, from infrastructure management to water resource monitoring, increasingly accurate knowledge of the gravitational field allows for improved measurement precision and the observation of phenomena that would otherwise remain invisible with other instruments. NASA's spectacular animation makes a complex concept accessible, but behind its visual power lies a wealth of data collected over fifteen years of space observations, destined to support many future applications of Earth sciences.

NASA's Geoid, the invisible map of gravity that redraws Earth

Here are three insights that might interest you:

A large-scale digital twin of the Earth will be born in Bologna
Space4Ocean Alliance, Space at the Service of the Oceans
ESA's Sodankylä supersite measures the changing Arctic