Optimizing MDX latitude/longitude query

Hi Darren,

I may need your help in tuning this one... this query takes more than a minute

WITH
    MEMBER [Measures].[Avg Latitude] AS
    ([Measures].[Cluster-Latitude-Avg] / [Measures].[01Exposure Values Count]) 
    MEMBER [Measures].[Avg Longitude] AS
    ([Measures].[Cluster-Longitude-Avg] / [Measures].[01Exposure Values Count]) 
SELECT
                 filter( nonempty 
                 (
                    [Location Rounding Cache].[Rounded_Longitude].[Rounded_Longitude]
                    *
[Location Rounding Cache].[Rounded_Latitude].[Rounded_Latitude] 
                 ),
                 (
                    [Measures].[t85_SPTL_LocationRoundingCache-Rounded_LatitudeMin] >= 34.141743
                    AND 
                    [Measures].[t85_SPTL_LocationRoundingCache-Rounded_LatitudeMax] <= 34.228566
                )
                AND 
                (
                    [Measures].[t85_SPTL_LocationRoundingCache-Rounded_LongitudeMin]  >= -92.127927
                    AND 
                    [Measures].[t85_SPTL_LocationRoundingCache-Rounded_LongitudeMax] <= -91.950359
                 )
            )
on rows,
{
    [Measures].[Cluster-ExposureDataSourceSID-Minimum],
    [Measures].[Cluster-LocationSID-Minimum],
    [Measures].[Avg Latitude], 
    [Measures].[Avg Longitude],
    [Measures].[01Exposure Values Count]
}
on columns
from c85_SPTL  
where 
    ([Location Rounding Cache].[SpatialRoundingCode Hieararchy].[SpatialRoundingCode].&[4] 

Many thanks