I have a thousands of records (lat,lng) on my java appengine and I'd like to generate a heatmap for it using [Android Heatmap Utility](https://developers.google.com/maps/documentation/android/utility/heatmap "Android Heatmap Utility"). However the raw data set is too big to be transferred via mobile network. How do you preprocess those records into something small enough so it can be transferred to the device?