Table 1.

Child node search direction strategy.

Θ	Keep 5 Directions	Abandon Direction
[337.5°, 360°) ∪ [0°, 22.5°)	000T, 045T, 090T, 270T, 315T	135T, 180T, 225T
[22.5°, 67.5°)	000T, 045T, 090T, 135T, 315T	180T, 225T, 270T
[67.5°, 112.5°)	000T, 045T, 090T, 135T, 180T	225T, 270T, 315T
[112.5°, 157.5°)	045T, 090T, 135T, 180T, 225T	270T, 315T, 000T
[157.5°, 202.5°)	090T, 135T, 180T, 225T, 270T	000T, 045T, 315T
[202.5°, 247.5°)	135T, 180T, 225T, 270T, 315T	000T, 045T, 090T
[247.5°, 292.5°)	180T, 225T, 270T, 315T, 000T	045T, 090T, 135T
[292.5°, 337.5°)	225T, 270T, 315T, 000T, 045T	090T, 135T, 180T