I wonder why healpix from NASA wasn't an option for them. Maybe the nonpermissive license...
H3: Uber’s Hexagonal Hierarchical Spatial Index (2018)
71–76 of 76 posts
Re: H3: Uber’s Hexagonal Hierarchical Spatial Index (2018)
#72Earlier quoted context omitted.
They go into some detail on this talk https://youtu.be/ay2uwtRO3QE?t=712 . What I get from their explanation is that hexagon is a better shape for map grids because they are the most complex shape that can tesselate (the other two are triangles and squares). As they are more close to a circle, distances within a cell are more stable, also computing the distance from a cell center to its neighbours is stable in hexago…
> hexagon is a better shape for map grids because they are the most complex shape that can tesselate [Penrose tiling intensifies]
Autocomplete of 'most compact'.
Re: H3: Uber’s Hexagonal Hierarchical Spatial Index (2018)
#73I hate Uber, but I now opened this issue suggesting a way to massively increase the performance of this anyway:
https://github.com/uber/h3/issues/258
(Note: by "massively" I mean pushing it to O(1) for the fundamental coordinate operations. So, perhaps read that as "most massively".)
Re: H3: Uber’s Hexagonal Hierarchical Spatial Index (2018)
#74Earlier quoted context omitted.
> I think from a technical point of view they made a poor choice. based on what criteria? H3 vs S2 is a tradeoff.
>> based on what criteria? Well for one, the fact that they don't nest properly. They mention that you can get the address of the parent hexagon by truncating that of the current one. The problem is that doesn't actually work all the way up because certain tiles on the border will flip back and forth in strange ways. They had to do something to deal with this, just like the would have had to do something else with sq…
Agreed,it seems incomprehensible that you would accept such nesting problems.
Re: H3: Uber’s Hexagonal Hierarchical Spatial Index (2018)
#75Why does each cell contain seven finer cells instead of six, resulting in imperfect containment?
You can't divide a hexagon into 6 regular hexagons, that would mean using triangular cells to subdivide the hexagon. Which isn't to say that you couldn't tile the planet with triangles, but they point out that the consistent relationship between neighboring hexagon tiles is useful: >Using a hexagon as the cell shape is critical for H3. As depicted in Figure 6, hexagons have only one distance between a hexagon centerp…
Thanks! It turns out I am bad at hexagons.
Re: H3: Uber’s Hexagonal Hierarchical Spatial Index (2018)
#76I might be the only one pedantically annoyed here, but... the very first image on this page contains a mix of hexagons and pentagons.
Which is it - an inaccurate image, and the system is really hexagon-based, or does the system also use pentagons? My guess is that it is actually all hexagon-based since the overlap between granularity is already only approximate.