From http://www.ngdc.noaa.gov/geomagmodels/struts/calcDeclination, the magnetic declinations of the sites varied from 12 11' to 12 17' east. To correct the magnetic azimuths of the sonics and props we'll use a declination value of 12.2 degrees for all sites.
To rotate the wind vectors, NIDAS uses the pointing angle of the sonic +V axis (Vazimuth), which is pointing azimuth of the sonic boom + 90, or the sonic +U axis - 90.
The following are from logbook entries of the sonic azimuths.
Note that all measured azimuths are in degrees magnetic, with the declination set to 0 on the compass or datascope, to reduce untraceable mental mistakes.
site |
log date |
pointing |
sonic boom azimuth, magnetic |
boom azimuth, true (mag+12.2) |
Vazimuth, true (boom+90) |
notes |
|---|---|---|---|---|---|---|
playa1 |
12/18 |
west |
76.9 + 180 = 256.9 |
269.1 |
359.1 |
|
playa1 |
1/5 |
" |
77.3+180 = 257.3 |
|
|
|
abc2 |
12/16 |
east |
249.5 - 180 = 69.5 |
81.7 |
171.7 |
|
abc2 |
1/4 |
" |
80 |
|
|
shot from the back (centered mast in claws), so hard to see; still thought it was okay |
hiland3 |
12/14 |
east |
249.5 - 180 = 69.5 |
81.7 |
171.7 |
|
hiland3 |
12/20 |
" |
253.5 - 180 = 73.5 |
85.7 |
175.7 |
|
hiland3 |
1/3 |
" |
254.2 - 180 = 74.2 |
|
|
shot from across the street |
wvally4 |
12/16 |
west |
86.7 + 180 = 266.7 |
278.9 |
8.9 |
|
wvally4 |
12/19 |
" |
80.3 + 180 = 260.3 |
272.5 |
2.5 |
mast was not lowered between 12/16 and 12/19 |
wvally4 |
12/20 |
" |
85.8 + 180 = 265.8 |
278.0 |
8.0 |
|
wvally4 |
1/3 |
" |
80.8 +180 = 260.8 |
|
|
|
eslope5 |
12/15 |
east |
248.7 - 180 = 68.7 |
80.9 |
170.9 |
|
eslope5 |
1/5 |
" |
251.1 - 180 = 71.1 |
|
|
|
wslope6 |
12/13 |
west |
77.8 + 180 = 257.8 |
270 |
0.0 |
|
wslope6 |
1/6 |
" |
79.3 |
|
|
|
river7 |
12/13 |
west |
85.5 + 180 = 265.5 |
277.7 |
7.7 |
|
Props
site |
log date |
pointing |
prop azimuth, magnetic |
prop az, true (mag+12.2) |
notes |
|---|---|---|---|---|---|
playa1 |
11/20 |
north |
|
1.0 |
|
playa1 |
12/18 |
north |
171.7 + 180 = 351.7 |
3.9 |
|
playa1 |
1/6 |
" |
174.2+180=354.2 |
6.4 |
|
wslope6 |
11/20 |
north |
|
1.7 |
should this have been -1.7, which agrees with 12/13? |
wslope6 |
12/13 |
north |
346.1 |
358.3 |
|
wslope6 |
1/6 |
" |
169.3+180=349.3 |
1.5 |
|