Method

Measurements were made along a 1 km by 3 km grid oriented orthogonal to the trend of the pass, at points separated by approximately 250 m in each direction of the grid. Positions and relative elevations were surveyed with an EDM instrument. Gravity measurements were made with a Worden gravity meter. Gravity measurements were corrected for drift by linear interpolation of base-station measurement made approximately every 2 hours. Average drift was about 0.25 mgals per 2 hours. Gravity was also corrected for relative elevation, but terrain corrections have not yet been applied.