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gishexagonal-architectureh3

H3 Geospatial Index's Projection and Aperture Selection

Interested in the H3 design.

From my understanding, the H3 is using azimuthal equidistant projection, which preserves distance and direction from a central point, but brings the area distortion.

H3 is trying to balance the area distortion and conformal distortion. However, based on this article (https://www.tandfonline.com/doi/full/10.1080/20964471.2022.2094926), https://www.tandfonline.com/doi/full/10.1080/20964471.2022.2094926 the area distortion is significant when compared with other grid systems.

So why not use the Lambert azimuthal equal-area projection similar to the ISEA (Icosahedral Snyder Equal Area)-based approaches?

Also curious about the hexagon hierarchical structure. There are several "Aperture" selections, such as 3,4,7,9. enter image description here

How do we define the "smooth" transition between resolutions? Is there any measurement?

Thanks.

BTW - Does that mean Uber's operation does not care about the cell's equal area across the whole global tessellation?

Solution

  • H3 uses icosahedral face-centered gnomonic projections. This is much faster than the ISEA projection, and projects great circle arcs to/from straight line segments. The system was designed for market place dynamics in individual cities, so equal area across the globe was not important.