jonatkins / s2-geometry-javascript Goto Github PK

We can now finally convert between S2CellId (uint64) and Hilbert Quadkey (``).

See

• http://stackoverflow.com/a/38625109/151312
• #9

However, we lack the support to go from from a key to lat / lng. It seems that once this.ij and this.st are calculated, we already know this.face (from either the key or id), so we can call the lat / lng method. However, we need to get those from the key/id somehow...

Once this is tested and has relevant documentation, it'll need a v1.0.0 tag for semver for use with npm, bower, or whatever else.

Where does one find 'L'?

Everyone is trying to implement their Pokemon GO clients in the browser, but if I could figure out what the 'L' is wrong with this library, I could take it to the browser, where it belongs. :D

In the meantime, I'm doing this: https://github.com/Daplie/node-pokemap/issues/1

Following Latitude and Longitute
lat = -6.120097
lng = 106.846511
return a Cell ID of '4197156086991552512'

Code:

var s2 = require('s2-geometry').S2;
var origin = s2.S2Cell.FromLatLng({lat: -6.120097, lng: 106.846511}, 15);
var cell = origin.toHilbertQuadkey();
console.log(s2.toId(origin));

Regards Skeec

Which license do you prefer? I'll add it and PR.

• MIT
• BSD 2-clause
• BSD 3-clause
• Apache-2.0
• ISC

I like to dual-license Apache-2.0 and MIT because then it can be GPL-compatible via MIT and also grant relevant rights in perpetuity all IP via Apache-2.0.

Do you know if it's possible to apply a hilbert curve without converting the cell to a 64-bit ID and back?

I'm able to return neighbors and I have some code for the hilbert curve and I'm trying to figure out how to adapt it so that I can add next() and prev() functions to a cell, but it appears to need and integer as initial.

I see you mention combine face,position to get the cell id L16, but I'm not sure which function that refers to and there's no variable called position, except in pointToHilbertQuadList L161 & L256, but I'm not clear on how to use that to get next and prev.

Can you help me with this at all? I'd be willing to pay for consulting.

Is it possible to directly derive a CellId, such as 9749618446378729472 from the face,quadtree pair, such as 4/032212303102210?

face encoding

• "human readable" form is base 10
• 3-bit - i.e. an unfolded 6-sided cube with base 10 face representations of 0,1,2,3,4,5
• 6 and 7 are unused and invalid
• 3 binary characters - i.e. 000, 001, 010, 011, 100, 101
• 110 and 111 are unused and invalid

position encoding

• "human readable" form is base 4 (quadkey)
• 61-bit

level encoding

• "human readable" form is base 10
• can calculated from the least (or most?) significant bit
• the length of hilbert curve quadkey / quadtree string is the level
• if the level is explicit then the extra digits are dropped or added (from / to the end?)

id encoding

Note that + means concat and NOT add

• face bits + position bits + 1 + pad(bits, 0)

// id          9749618446378729472
// quadkey     4/032212303102210
// base 4      10    032212303102210                   1000000000000000
// base 10    100    001110100110110011010010100100    1000000000000000000000000000000

Note that + means concat and NOT add

// psuedo-code
// This WON'T work because JavaScript uses 31-bit integers (53-bit floats)
var faceBits = 3;
var maxLevel = 30;
var maxBits = (maxLevel * 2) + 1; // one bit is lost to the marker

var str = face.toString(2) + position.toString(2) + '1';
str = padRight(str, maxBits, '0');
//  4/032212303102210
//  4    032212303102210                    1000000000000000
// 100   0001110100110110011010010100100    1000000000000000000000000000000

Long.fromString('9749618446378729472', true, 10).toString('4');
'20131031212211021000000000000000'

Long.fromString('9749618446378729472', true, 10).toString('2');
'1000011101001101100110100101001001000000000000000000000000000000'

Expected:

9749618446378729472
20131031212211021000000000000000
1000011101001101100110100101001001000000000000000000000000000000

I'm currently hosting the updates at https://github.com/coolaj86/s2-geometry-javascript

Would you like to transfer ownership?

You can go to the transfer ownership section at the bottom of the settings page, click 'transfer' and choose to transfer s2-geometry-javascript to Daplie.

I've already created AUTHORS and LICENSE files in my fork to give you proper attribution.

Once we have a license I'll create the package.json and publish (and add you as owner if you have an npm username)