Patch Test

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Despite the careful measurements of transducer alignments and offsets, the true geometry of the installed system can only be determined through the determination of the self-consistency of lake floor measurements. A full patch test procedure to check for proper system alignments and to calibrate any time delay and gyro misalignment was completed at Lake Tahoe, California a week prior to our arrival at Crater Lake . The EM1002 data were directly compared to data collected in Lake Tahoe during the 1998 mapping (Gardner et al., 1998; 2000). The static adjustments were determined from the patch test and entered into the Simrad software. We also conducted a series of patch tests once the boat was in Crater Lake whereby the system was run back and forth across both a flat area and a steep slope of the lake floor to determine if there were residual roll, pitch, heading, or timing offsets that required correction factors.