pheelicks
Joined 15 years ago
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Nov 24
@pheeelicks on twitter (yes, 3 e's)
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Comment · 7 months ago
A5 - a pentagonal geospatial index: https://a5geo.org
If you’ve used H3 the semantics should be familiar. The biggest differentiator is the fact that cells have exactly the same area globally, for why this matters see: https://a5geo.org/docs/recipes/a5-vs-h3
Since starting the project last year and providing implementations in TypeScript, Python and Rust it’s been great to see a community grow, porting or integrating into DuckDB, QGIS and many more: https://a5geo.org/docs/ecosystem
Comment · 1 year ago
Nice library. Without trying to start the classic geo-flamewar, do you consider returning the DD coordinates as [longitude, latitude]? This is in line with a number of formats out there, including the popular GeoJSON that is often used in JavaScript apps.
Getting these backwards is a common frustration, so my vote would be for Lon/lat ordering.
Regardless of which you choose, I find DD to be quite cryptic and it would be nicer to spell out the order, eg parseToLonLat - then the order is clear to the user
Comment · 1 year ago
It is a common misconception that h3 is equal area. At any resolution level the cell size varies by a factor of 2, which is (roughly) the same as S2.
See the following visualizations for an illustration:
Comment · 1 year ago
Very impressive results, cool to see innovation in this space! I’d definitely be interested in a follow up post going into the details of the geometric algorithms.
I’m working on my own DGGS, A5, the first (and only) to use pentagons. It offers true equal area cells and a much higher cell fidelity (below 1cm compared to 1m for H3).
I’m looking for contributors to get involved and you seem to have the perfect skill set. It would be amazing to have you join the project :) https://a5geo.org/ https://github.com/felixpalmer/a5
Comment · 1 year ago
This agrees with my experience on a project I’ve been working on this year, in particular related to porting the code. I’ve developed a strategy that I’m calling “Polyglot Mirroring” where the code is written in multiple languages at once, with LLMs handling the mirroring.
I actually made a Ask HN about it just today https://news.ycombinator.com/item?id=45091607 but for some reason the HN algorithm never even showed it on the Ask page :/
Comment · 1 year ago
https://news.ycombinator.com/item?id=43971314 got some attention here, when I originally released the TypeScript version, so following up with the news that the library has now been entirely ported to Python.
Not only is this an implementation of the library in a language that is better suited to data science, but there are also many improvements to the underlying A5 grid since the original launch, in particular a true equal area projection, which even accounts for the ellipsoidal shape of the earth. https://a5geo.org/examples/area
To get started, take a look at https://a5geo.org/docs/quickstart/python
Comment · 1 year ago
My mistake, you are correct. The base solid is indeed the rhombic dodecahedron. I believe the point about the angular defect is still valid though.
Comment · 1 year ago
Yes, such indices (S2 & H3) are widely used for providing a index in databases, so geospatial features that are close by in the world and stored in nearby databases rows. https://cloud.google.com/bigquery/docs/grid-systems-spatial-...