Transverse Cylindrical Equal Area Projection
Sep 24,2026

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Introduction

Transverse Cylindrical Equal Area Projection is a type of map projection that uses a transversely oriented cylindrical surface as the projection surface, projecting the graticule of the Earth's ellipsoid onto the cylindrical surface under equal-area conditions and then unrolling it into a plane. Its cylinder axis is perpendicular to the Earth's axis of rotation, and the cylindrical surface is typically made tangent to a specific meridian of the Earth. This tangent central meridian appears as a straight line after projection and maintains equal-area, distortion-free characteristics. The Equator is a straight line perpendicular to the central meridian, and all other meridians and parallels are symmetrically distributed curves. This type of projection strictly ensures that the area ratio of regions before and after projection remains exactly consistent, producing no area distortion. It is often used in thematic mapping scenarios that require precise statistical analysis of regional areas.

Projection Basic

The Transverse Cylindrical Equal Area Projection works by placing the cylindrical surface transversely, with the cylinder's axis perpendicular to the Earth's axis of rotation, making the cylindrical surface tangent to a specific meridian of the Earth. This tangent meridian serves as the central meridian. Strictly following the mathematical constraint of equal area, the entire graticule on the Earth's ellipsoid is projected onto the lateral surface of the cylinder, which is then cut along a generatrix and unrolled into a plane. In the final projection result, the tangent central meridian and the Equator orthogonal to it both appear as straight lines, while all other meridians and parallels are curves symmetrically distributed about the central meridian and the Equator. Throughout the process, the area of any region before and after projection remains exactly equal, producing no area distortion.

Pros

Equal-area property: The area of any region before and after projection is strictly equal, with no area distortion, making it suitable for thematic mapping that requires precise statistical analysis and comparison of regional areas.
Good central meridian control: With the central meridian as the reference, length and shape distortion are relatively small in the band-shaped region extending north-south near it.
Flexible and adjustable: The position of the central meridian can be adjusted, or a secant arrangement can be used, to accommodate mapping needs across different longitude ranges.
Authentic representation of features: Accurately reflects the relative size relationships of geographic features, benefiting statistical thematic maps such as resource distribution and population density.

Cons

Authentic representation of features: Accurately reflects the relative size relationships of geographic features, benefiting statistical thematic maps such as resource distribution and population density.
Severe stretching at high latitudes: Length distortion increases sharply in high-latitude regions, and maps near the polar regions are severely distorted, resulting in poor practicality.
Complex graticule: Except for the central meridian and the Equator, all lines are complex curves, increasing the difficulty of map production, coordinate reading, and measurement.
Narrow application range: In actual production, it is far less widely used than the Gauss-Krüger projection and the UTM projection, with fewer use cases.

Application Scenario

The Transverse Cylindrical Equal Area Projection is mainly applied in thematic mapping fields that require strict preservation of area accuracy, such as population density distribution maps at global or regional scales, land use and cover area statistical maps, and natural resource and ecological environment distribution thematic maps. It is also often used in the compilation of large-scale or medium-scale thematic maps for north-south elongated mid-latitude band regions to ensure area authenticity near the central meridian. However, because of its relatively large angular distortion and its far less widespread practical application compared to the Gauss-Krüger projection, it is typically selected only in special mapping scenarios where area accuracy is a rigid requirement while shape accuracy is not critical.