Abstract
Our company began the dam displacement monitoring by GPS system applied in Numahara dam located in the Tochigi Prefecture since September, 2007. It aimed to verify the applicability of GPS in snow area, and to compare to traditional collimation method. As a result, the GPS data was high accuracy, although the sensor icing and the frost heaving occurred. And the GPS measured the detail displacement of dam during evacuation and re-storage, which could hardly measure by collimation.
