Table 2. Useless ratio of Feature points.

Zone	L-15	L-30	R-15	R-30	D	U
1	22.5	27.5	22.5	27.5	37.5	30
2	23.1	28.2	25.6	28.2	35.9	33.3
3	25	50	33.3	33.3	16.7	25
4	16.7	50	50	33.3	8.3	33.3
5	28.6	28.6	21.4	35.7	35.7	28.6
6	27.3	27.3	27.3	36.4	36.4	36.4