TMS tiling scheme 

geotrellis.spark.tiling - utility methods to convert from geo coords to tile ids and back
geotrellis.spark.formats - hadoop writable types for tile id and arrays. The latter will eventually be replaced by RasterData or something similar but the idea of convert to Writable will stay same
geotrellis.spark.ArgHadoopDriver - a driver that illustrates how all the above fit together