The new regional scoring grid for Ingress (Regional Scoring – This Changes Everything – DeCode Ingress) is based on an S2 (Hilbert curve) global grid as used in Geometry on the Sphere: Google's S2 Library and an encoding described in request: regional scoring cell borders · Issue #741 · jonatkins/ingress-intel-total-conversion.
That allows every point in the world to be mapped to a point along the Hilbert curve, and begs existential questions like:
- Where does the region s2 / hilbert curve start for the Americas face (AM)?
- Where does it end?
- How do the 6 faces of the cube line up?
- Is there a good argument for a well-defined start to the whole curve? On which face?
And, for extra credit, to go to the limit, the whole enchilada: what is the sequence of all Ingress portals by Hilbert curve order (adding additional levels as necessary)? 🙂
Best Answer
OK, the S2map presentation linked does a pretty good job of explaining things, but it lacks a good visualisation of the whole earth.
IITC now has a scoring cells plugin that'll give you a nice interactive map of all the cells, and http://ingress-cells.appspot.com/ will let you search individual cells and click to find out the names without touching IITC if you're wary of the Niantic TOS.
It's worth noting that the cells are only numbered along the hilbert curve at the lowest level, i.e. the final two digits - AM01 through AM16 are 'rows' reaching across the AM face (numbered north to south), and AM**-ALPHA through AM**-SIERRA are 'columns' reaching down the AM face, numbered west to east (n.b. this orientation changes for each face!). Therefore each face isn't really a complete Hilbert Curve
With that in mind:
As for listing portals in 'cell order' - well that would be scraping the intel map and definitely a breach of the Niantic TOS ;-)
Postscript: Not all the NATO Phonetic Alphabet labels are used in 'column' names, here's the list:
ALPHA, BRAVO, CHARLIE, DELTA, ECHO, FOXTROT, GOLF, HOTEL, JULIET, KILO, LIMA, MIKE, NOVEMBER, PAPA, ROMEO, SIERRA
Excluded: Indigo, Oscar, Quebec - draw your own conclusions as to why!