Golf ball

1. A golf ball comprising a core, a mid layer positioned outside the core, and a cover positioned outside the mid layer, wherein

the golf ball satisfies mathematical formulas (1) to (3) shown below,

a large number of dimples are provided on a surface of the golf ball,

when the surface is divided into a northern hemisphere and a southern hemisphere, each of the hemispheres includes a high-latitude region, a mid-latitude region and a low-latitude region,

the high-latitude region has a latitude range of equal to or greater than 40° but equal to or less than 90°,

the mid-latitude region has a latitude range of equal to or greater than 20° but less than 40°, and

the low-latitude region has a latitude range of equal to or greater than 0° but less than 20°,

one plane can divide the hemisphere dimple pattern into divided dimple patterns that have mirror symmetry with respect to each other,

the high-latitude region has a dimple pattern that is not rotationally symmetrical, and

the low-latitude region has a dimple pattern that is not rotationally symmetrical, and

formulas (1) to (3) are as follows:

Hc≦ 49  (1)

Hm−Hc≧ 15  (2)

Hm−Hb≦ 2  (3)

wherein Hm represents a Shore D hardness of the mid layer, He represents a Shore D hardness of the cover, and Hb represents a Shore D hardness of the surface of the golf ball.

2. The golf ball according to claim 1 , wherein

the mid layer is formed from a resin composition, and a principal component of a base resin of the resin composition is an ionomer resin, and

the cover is formed from a resin composition, and a principal component of a base resin of the resin composition is a polyurethane.

3. The golf ball according to claim 1 , wherein the cover has a thickness Tc of equal to or less than 0.8 mm.

4. The golf ball according to claim 3 , wherein the thickness Tc of the cover is equal to greater than 0.3 mm but equal to or less than 0.5 mm.

5. The golf ball according to claim 1 , wherein the hardness Hm is equal to or greater than 55.

6. The golf ball according to claim 1 , wherein the golf ball satisfies mathematical formula (4) below:

0.6≦( Hm−Ho )/ Hc≦ 1.5  (4)

wherein Hm represents a Shore D hardness of the mid layer, Ho represents a Shore D hardness at a central point of the core, and He represents a Shore D hardness of the cover.

7. The golf ball according to claim 1 , wherein the golf ball satisfies mathematical formula (5) below:

Hm−Ho≧ 20  (5)

wherein Hm represents a Shore D hardness of the mid layer, and Ho represents a Shore D hardness at a central point of the core.

8. The golf ball according to claim 1 , wherein the mid-latitude region dimple pattern is not rotationally symmetrical.

9. The golf ball according to claim 1 , wherein

the high-latitude region includes a pole vicinity region,

the pole vicinity region has a latitude range of equal to or greater than 75° but equal to or less than 90°, and

the pole vicinity region dimple pattern is rotationally symmetrical.

10. The golf ball according to claim 1 , wherein

the low-latitude region includes an equator vicinity region,

the equator vicinity region has a latitude range of equal to or greater than 0° but less than 10°, and

the equator vicinity region dimple pattern is rotationally symmetrical.

11. The golf ball according to claim 1 , wherein a great circle that does not intersect any dimple does not exist on the surface.

12. The golf ball according to claim 1 , wherein a ratio of a total area of the dimples to a surface area of a phantom sphere of the golf ball is equal to or greater than 80%.

13. The golf ball according to claim 9 , wherein the pole vicinity region rotational angle is 60°, 72°, 90° or 120°.

14. The golf ball according to claim 10 , wherein the equator vicinity region rotational angle is 60°, 72°, 90° or 120°.