雑に書いた
地球は周囲40,075Km
Quadkey
| ズームレベル（Quadkey桁数） | タイル一辺の距離[Km] | [m] |
|---|---|---|
| 0 | 40,075[Km] | 40,075017[m] |
| 1 | 20,037[Km] | 20,037508[m] |
| 2 | 10,018[Km] | 10,018754[m] |
| 3 | 5,009[Km] | 5,009377.1[m] |
| 4 | 2,504[Km] | 2,504688.5[m] |
| 5 | 1,252[Km] | 1,252344.3[m] |
| 6 | 626.1[Km] | 626172.1[m] |
| 7 | 313.0[Km] | 313086.1[m] |
| 8 | 156.5[Km] | 156543[m] |
| 9 | 78.2[Km] | 78271.5[m] |
| 10 | 39.1[Km] | 39135.8[m] |
| 11 | 19.5[Km] | 19567.9[m] |
| 12 | 9.78[Km] | 9783.94[m] |
| 13 | 4.89[Km] | 4891.97[m] |
| 14 | 2.44[Km] | 2445.98[m] |
| 15 | 1.22[Km] | 1222.99[m] |
| 16 | 0.611[Km] | 611.496[m] |
| 17 | 0.305[Km] | 305.748[m] |
| 18 | 0.152[Km] | 152.874[m] |
| 19 | 0.076[Km] | 76.437[m] |
| 20 | 0.038[Km] | 38.2185[m] |
| 21 | 0.019[Km] | 19.10926[m] |
| 22 | 0.009[Km] | 9.55463[m] |
| 23 | 0.004[Km] | 4.777315[m] |
| 24 | 0.002[Km] | 2.3886575[m] |
Km = 40,075[Km] / 2^zoomLevel
Quadkey16桁の精度は0.611[Km]
もし2点間の距離をざっくりとでも求めたい場合（非推奨）
A = 11011011011011011111
B = 11011011011011022222
110110110110110の15桁は一致しているので
1辺の長さは1.22km
直角三角形斜辺の長さ = 辺 × 辺 × √2 より
3.45068 = 1.22×1.22×√2
この2つの距離は0<x<3.45068[Km]の範囲内にあると分かる
注意
A = 011111111111111111111
B = 100000000000000000000
は隣どうしだが，上記の方法で計算すると範囲は広くなる