In September, 2009, Geotech Ltd. carried out a helicopter-borne geophysical survey for Pebble Partnership over the Pebble Property situated in the Bristol Bay region of southwest Alaska, approximately 320 km southwest of Anchorage. Principal geophysical sensors included the Z-axis Tipper Electromagnetic (ZTEM) system and caesium magnetometer. A total of 250 km were flown at a nominal line-spacing of 200m over a 60 km2 area. The objective of the ZTEM survey was test its ability to map the Pebble porphyry deposit from surface to depth, based on resistivity contrasts.