php数据问题，请教高手！
有这样一个数组：
Array
(
[0] => Array
(
[time] => 1382060855000
[day] => 2013-10-18
[latitude] => 39.9289
[longitude] => 116.3883
)
[1] => Array
(
[time] => 1382060855000
[day] => 2013-10-18
[latitude] => 42
[longitude] => 43.5
)
[2] => Array
(
[time] => 1382060855000
[day] => 2013-10-18
[latitude] => 38.9122
[longitude] => 121.6022
)
[3] => Array
(
[time] => 1382060855000
[day] => 2013-10-18
[latitude] => 40.5525
[longitude] => -74.2915
)
[4] => Array
(
[time] => 1382060855000
[day] => 2013-10-18
[latitude] => 40.5525
[longitude] => -74.2915
)
[5] => Array
(
[time] => 1382060855000
[day] => 2013-10-18
[latitude] => 38.9122
[longitude] => 121.6022
)
[6] => Array
(
[time] => 1382060855000
[day] => 2013-10-18
[latitude] => 38.9122
[longitude] => 121.6022
)
)
里面的经纬度有重复的数据，想过滤掉重复数据，并且得到每一个相同经纬度的数量。最后得到的数组如下：
这个要怎么实现呢？
php 数组
