Trying to Sort this Multi-Dimentional Array

I have a multi-dimentional array.. please see a small sample of my array below..

I have been messing with this for ages but can't seem to find a decent solution that doesn't involve an awful lot of loops.

I want to sort the top set of elements ie. the [ED], [ER] etc.. but by using an element that is a couple of levels down.
eg. sort using all the elements [??][poi_base][data]

========Array Follows ==========
Array
(
[ED] => Array
(
[poi_base] => Array
(
[data] => 6.596273292
[data_exception_d] => 0
[id_d] => 4171
)

[poi_currentPeriod] => Array
(
[data] => 6.404968944
[data_exception_d] => 0
[id_d] => 5231
)

)

[ER] => Array
(
[poi_base] => Array
(
[data] => 8.128529388
[data_exception_d] => 0
[id_d] => 4172
)

[poi_currentPeriod] => Array
(
[data] => 8.714440998
[data_exception_d] => 0
[id_d] => 5232
)

)

[HA] => Array
(
[poi_base] => Array
(
[data] => 9.662311461
[data_exception_d] => 0
[id_d] => 4173
)

[poi_currentPeriod] => Array
(
[data] => 9.20357383
[data_exception_d] => 0
[id_d] => 5233
)

)

[HO] => Array
(
[poi_base] => Array
(
[data] => 12.38185255
[data_exception_d] => 0
[id_d] => 4174
)

[poi_currentPeriod] => Array
(
[data] => 12.92672078
[data_exception_d] => 0
[id_d] => 5234
)

)

[LA] => Array
(
[poi_base] => Array
(
[data] => 19.62699551
[data_exception_d] => 0
[id_d] => 4175
)

[poi_currentPeriod] => Array
(
[data] => 19.26375874
[data_exception_d] => 0
[id_d] => 5235
)

)

[NO] => Array
(
[poi_base] => Array
(
[data] => 8.396535581
[data_exception_d] => 0
[id_d] => 4176
)

[poi_currentPeriod] => Array
(
[data] => 6.514513109
[data_exception_d] => 0
[id_d] => 5236
)

)

[PE] => Array
(
[poi_base] => Array
(
[data] => 9.164309715
[data_exception_d] => 0
[id_d] => 4177
)

[poi_currentPeriod] => Array
(
[data] => 8.680832548
[data_exception_d] => 0
[id_d] => 5237
)

)

[SE] => Array
(
[poi_base] => Array
(
[data] => 5.653142898
[data_exception_d] => 0
[id_d] => 4178
)

[poi_currentPeriod] => Array
(
[data] => 5.260130844
[data_exception_d] => 0
[id_d] => 5238
)

)

[SU] => Array
(
[poi_base] => Array
(
[data] => 1.841180927
[data_exception_d] => 0
[id_d] => 4179
)

[poi_currentPeriod] => Array
(
[data] => 1.976629399
[data_exception_d] => 0
[id_d] => 5239
)

)

[YA] => Array
(
[poi_base] => Array
(
[data] => 6.958865581
[data_exception_d] => 0
[id_d] => 4180
)

[poi_currentPeriod] => Array
(
[data] => 7.387788585
[data_exception_d] => 0
[id_d] => 5240
)

)

)

 

Please indent it, it is hard to read.