Uber H3: Uber’s Hexagonal Hierarchical Spatial Index

概述

Uber H3

H3是一个针对地球的空间划分和空间索引系统。

The H3 geospatial indexing system is a discrete global grid system consisting of a multi-precision hexagonal tiling of the sphere with hierarchical indexes. The hexagonal grid system is created on the planar faces of a sphere-circumscribed icosahedron, and the grid cells are then projected to the surface of the sphere using an inverse face-centered polyhedral gnomonic projection.

名词解释

Icosahedron（正二十面体）

正二十面体(Regular twenty aspect) 是由20个等边三角形所组成的正多面体，共有12个顶点，30条棱，20个面。为五个柏拉图多面体之一。

In geometry, an icosahedron is a polyhedron with 20 faces.

Hexagons（正六边形）

正六边形就是在平面几何学中，具有六条相等的边和六个相等内角的多边形。各内角相等，六边相等。由多边形外角和等于360度，推出一个内角为180-(360/6)=120度，所以内角为120度。

Gnomonic projection

It views the the surface data from the center of the earth.

• The gnomonic map projection displays all great circles as straight lines.
• The least distortion occurs at the tangent point.
• Less than half of the sphere can be projected onto a finite map.
• Since Meridians and the Equator are great circles, they are always shown as straight lines.

dymaxion projection(Fuller Map)

用一个正二十面体内切地球，并且是多面体的顶点均映射到海洋区域，然后将地球使用Gnomonic projection 投影到多面体上，将多面体展成一个平面，保证大陆不会被分裂开。

A map of the Earth which presents geographic information in a single, comprehensive picture without breaks in any of the continental contours, or any visiUberble distortion of the relative shapes or sizes of the land masses.

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