### Introduction

Theory of Heiskenen, developed by the Finnish geophysicist Veikko Aleksanteri Heiskanen in 1933, is a fundamental geodetic theory that explains the Earthâ€™s gravity field and its variations. The theory provides a mathematical model that relates the gravity field to the distribution of mass within the Earth.

Heiskanenâ€™s theory is based on the principle that the Earthâ€™s gravity field is caused by the distribution of mass within the Earth. The theory proposes that the Earthâ€™s gravity field can be represented by a geoid, which is a hypothetical surface that would coincide with mean sea level if the Earth were completely covered by water. The geoid is not perfectly spherical, but rather has undulations and irregularities that reflect the uneven distribution of mass within the Earth.

### Theory of Heiskenen (1933)

The Heiskanen theory, also known as the gravitational geoid theory, is a geodetic theory developed by the Finnish geophysicist Veikko Aleksanteri Heiskanen in 1933. The theory provides a mathematical model for the Earthâ€™s gravity field and its variations.

The Heiskanen theory is based on the principle that the Earthâ€™s gravity field is caused by the distribution of mass within the Earth. According to this theory, the Earthâ€™s gravity field can be represented by a geoid, which is a hypothetical surface that would coincide with mean sea level if the Earth were completely covered by water. The geoid is not perfectly spherical, but rather has undulations and irregularities that reflect the uneven distribution of mass within the Earth.

Heiskanenâ€™s theory provides a mathematical framework for determining the shape of the geoid and its variations. It takes into account various factors such as the Earthâ€™s rotation, its ellipsoidal shape, and the distribution of mass within the Earth. The theory is used in geodesy, which is the study of the Earthâ€™s shape, size, and gravity field, to measure the Earthâ€™s topography and variations in gravity.

To further elaborate, the Heiskanen theory provides a mathematical framework for determining the shape of the geoid and its variations through a mathematical model that relates the gravity field to the distribution of mass within the Earth. The theory takes into account the Earthâ€™s rotation, which results in a centrifugal force that causes the equatorial region to bulge out and the poles to flatten.

The theory also considers the Earthâ€™s ellipsoidal shape, which is caused by its rotation, and the distribution of mass within the Earth, which affects the gravity field. The variation in the gravity field can be caused by variations in the Earthâ€™s density and topography.

The Heiskanen theory is widely used in geodesy to measure the Earthâ€™s topography and variations in gravity. It has played a key role in many important applications such as satellite geodesy, which uses artificial satellites to measure the Earthâ€™s gravity field, and global positioning systems (GPS), which uses a network of satellites to determine the precise location of points on the Earthâ€™s surface.

Overall, the Heiskanen theory has been a fundamental contribution to geodetic science, and it continues to be used as a basis for many applications in geodesy, geophysics, and other related fields.

### Important Facts About Theory of Heiskenen (1933)

Here are some important facts about the Heiskanen theory (1933):

- The Heiskanen theory is also known as the gravitational geoid theory.
- The theory provides a mathematical model that relates the Earthâ€™s gravity field to the distribution of mass within the Earth.
- The theory proposes that the Earthâ€™s gravity field can be represented by a geoid, which is a hypothetical surface that would coincide with mean sea level if the Earth were completely covered by water.
- The geoid is not perfectly spherical, but rather has undulations and irregularities that reflect the uneven distribution of mass within the Earth.
- The Heiskanen theory takes into account various factors such as the Earthâ€™s rotation, its ellipsoidal shape, and the distribution of mass within the Earth.
- The theory is widely used in geodesy to measure the Earthâ€™s topography and variations in gravity.
- The theory has played a key role in many important applications such as satellite geodesy and global positioning systems (GPS).
- The Heiskanen theory is still widely used as a basis for many applications in geodesy, geophysics, and other related fields.
- The theory has been expanded upon and refined by subsequent researchers over the years, leading to new insights and applications.
- The Heiskanen theory has contributed significantly to our understanding of the Earthâ€™s gravity field and its variations, and it remains an important foundation for the study of the Earthâ€™s shape, size, and gravity field.
- The Heiskanen theory is named after Veikko Aleksanteri Heiskanen, a Finnish geophysicist who first proposed the theory in 1933.
- The Heiskanen theory was one of the first comprehensive theories of the Earthâ€™s gravity field, and it provided a significant advance in our understanding of the Earthâ€™s shape and gravity field.
- The Heiskanen theory takes into account the effects of the Earthâ€™s rotation on the gravity field, which causes the equatorial region to bulge out and the poles to flatten.
- The Heiskanen theory has been refined over the years by subsequent researchers, and newer models such as the EGM2008 (Earth Gravity Model 2008) have been developed that provide more accurate measurements of the Earthâ€™s gravity field.
- The Heiskanen theory has been used in a wide range of applications, including satellite gravity missions such as the Gravity Recovery and Climate Experiment (GRACE) and its follow-up mission, GRACE-FO, which are used to measure changes in the Earthâ€™s gravity field.
- The Heiskanen theory has also been used to study the Earthâ€™s interior structure, including the mantle and core, by analyzing the gravity field variations caused by density differences within the Earth.
- The Heiskanen theory has played a key role in the development of global geodetic reference frames such as the International Terrestrial Reference Frame (ITRF), which is used to define the positions of points on the Earthâ€™s surface with respect to a fixed reference frame.
- The Heiskanen theory has also been used to study the dynamics of the Earthâ€™s crust, including plate tectonics, by analyzing the variations in the gravity field caused by changes in the Earthâ€™s topography.
- The Heiskanen theory is a foundational theory in geodesy, and it continues to be used as a basis for many applications in geodetic science, including navigation, mapping, and geophysical exploration.
- The Heiskanen theory has contributed significantly to our understanding of the Earthâ€™s shape, size, and gravity field, and it remains an important area of research in geodetic science and geophysics.

### Conclusion

Heiskanen theory developed by the Finnish geophysicist Veikko Aleksanteri Heiskanen in 1933 is a fundamental geodetic theory that explains the Earthâ€™s gravity field and its variations. The theory provides a mathematical model that relates the gravity field to the distribution of mass within the Earth, and proposes that the Earthâ€™s gravity field can be represented by a geoid, which is a hypothetical surface that would coincide with mean sea level if the Earth were completely covered by water. The theory takes into account various factors such as the Earthâ€™s rotation, its ellipsoidal shape, and the distribution of mass within the Earth, and it has contributed significantly to our understanding of the Earthâ€™s gravity field and its variations. The Heiskanen theory has played a key role in many important applications such as satellite geodesy and global positioning systems (GPS), and it continues to be used as a basis for many applications in geodesy, geophysics, and other related fields.