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Note: Aug15.  Triginometric Sanity Check:

SteveO, Chenning, Khuong, and I setup a reference line parallel to array, with a perpendicular from the NE most rohn tower to a point 75.59m to a stake on that parallel line.   We used triangles from the array to establish the perpendicular, and from the reference stake used the theadolite theodolite to shoot the parallel line.  We determined the distance to the stake by triangulation using the theadolite theodolite setup on the parallel 100' away from the reference and shooting back to the rohn tower.    From this reference stake and reference line, we aligned the theadolite theodolite to the upwind sonics and measured the distance D from the stake to the alignment point.   Using these dimension, adjusting the 75.59 distance to 72.47 by the 3.12m difference from the rohn to the pam tripod and subtracting the .43 sonic spacing and 1.87m offset of the tripod to the rohn tower (for D'), we took the asine and added the array alignment (325-180=145deg true looking back toward the sonics) to determine the sonic angles; and substracted 13.6 for the magnetic declination.  Note we visually aligned to the sonics using the "Horst method" which balances the back two transducers on either side of the square sonic head assembly.   This technique should work, although for the upwind array in particular there are several tolerance assumptions that we can't measure directly (ie the 1.87, 3.12, etc) which makes it a bit awkward.   Note the sunangle readings for u7 were within .1 deg, but for u11 it was 1deg (Chris used the 'front transducer alignment method which could account for a slight additional difference).

cal: azimuth entered in cal_file = BoomDirMagn - 131.7

Later in the day I took readings for the Horizontal Array.   In this case 'D' is the distance from the reference stake to the SW direction (positive).   The distance from the rohm tower leg to the  first sonic was measured as .6m, and the length of the boom to the head bolt as 1.37m, the sonic spacing is .43m.   D' = D - the index number (sonic#-1) * .43m.   The angle is asine (D' /  (75.59 - 1.37))