←back to thread

Show HN: A5

(github.com)
95 points pheelicks | 1 comments | 13 May 25 10:02 UTC | HN request time: 0.213s | source
Show context
xioxox ◴[13 May 25 15:36 UTC] No.43974102[source]▶
What's the advantage of this over HEALPix projection? https://en.wikipedia.org/wiki/HEALPix
replies(2): >>43975085 #>>43975193 #
michelpp ◴[13 May 25 17:07 UTC] No.43975193[source]▶
I'm not sure about A5, but I do know that HEALPix cell boundaries are not geodesics, whereas S2 cells are always bounded by four geodesics.
replies(1): >>43975624 #
1. pheelicks ◴[13 May 25 17:44 UTC] No.43975624[source]▶
A5 cell boundaries are geodesics. One more difference that I thought of is that HEALPix is generally not aligned with the continents (makes sense as it is mostly used for astrophysics), whereas the hilbert curve used to index A5 is aligned with the continental land masses: https://a5geo.org/examples/globe

As a result, when A5 is used as a spatial index, it will generally not have jumps in the cell index values when querying nearby locations on land