Sphere2Vec: Multi-Scale Representation Learning over a Spherical Surface for Geospatial Predictions
This solves the distortion issue for geospatial predictions on Earth's surface, which is incremental as it builds on prior multi-scale encoding methods.
The paper tackled the problem of map projection distortion in location encoding for large-scale GPS datasets by proposing Sphere2Vec, a model that encodes points directly on a spherical surface, and it outperformed existing 2D space encoders, particularly in polar regions and data-sparse areas for geo-aware image classification tasks.
Generating learning-friendly representations for points in a 2D space is a fundamental and long-standing problem in machine learning. Recently, multi-scale encoding schemes (such as Space2Vec) were proposed to directly encode any point in 2D space as a high-dimensional vector, and has been successfully applied to various (geo)spatial prediction tasks. However, a map projection distortion problem rises when applying location encoding models to large-scale real-world GPS coordinate datasets (e.g., species images taken all over the world) - all current location encoding models are designed for encoding points in a 2D (Euclidean) space but not on a spherical surface, e.g., earth surface. To solve this problem, we propose a multi-scale location encoding model called Sphere2V ec which directly encodes point coordinates on a spherical surface while avoiding the mapprojection distortion problem. We provide theoretical proof that the Sphere2Vec encoding preserves the spherical surface distance between any two points. We also developed a unified view of distance-reserving encoding on spheres based on the Double Fourier Sphere (DFS). We apply Sphere2V ec to the geo-aware image classification task. Our analysis shows that Sphere2V ec outperforms other 2D space location encoder models especially on the polar regions and data-sparse areas for image classification tasks because of its nature for spherical surface distance preservation.