Two coordinate systems have been defined:

absolute coordinate system (lab frame)
local coordinate system (dependent on the subdetector)

The absolute coordinate system is identified by (x,y,z), the local system by (iu, iv, sensor_iU, sensor_iV, iLayer) where

iLayer is the index of the silicon wafer layer, start counting from the one closer to the beam
sensor_iU and sensor_iV are the coordinates of the silicon wafer in the layer
iu and iv are the coordinates of the silicon cell within the wafer

Conversion between the local system and the lab frame is done by HGCalTBCellVertices

Sensors in odd and even layers are rotated around the y axis, the local coordinate system is NOT rotated, the relation between the local system and the lab frame are always the same. So the calibration pads in odd and even layers are in different (iu, iv) positions. This is taken into account by the conversion between electronic ID and detId in the HGCalTBRawToDigi