Changes between Version 5 and Version 6 of Processing/LeverArmOffset
 Timestamp:
 Dec 18, 2008 3:24:23 PM (10 years ago)
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Processing/LeverArmOffset
v5 v6 7 7 The distance is from the phase centre of the master (rear) antenna to each sensor's "prime" point; so for the ATM it is the scan mirror centre, for the Eagle, Hawk and CASI ideally the focus point of the lens. 8 8 9 The angles (as used in aznav) are: gamma is the positive angle from the horizontal through the antenna to the sensor prime point and delta is positive to starboard from the centre line direction of the aircraft.9 The angles (as used in aznav) are: gamma is the positive angle from the vertical through the antenna to the sensor prime point and delta is positive to starboard from the centre line direction of the aircraft. 10 10 11 11 Initially it is necessary to make sure you have the correct sensor prime point coords as observed. … … 14 14 15 15  16 Jan 2008 numbers: 16 18th Dec. 2008: Due to confusion about angle directions, the originally computed gamma angles are incorrect. The error caused should be of similar magnitude to the previous, similar error (ie ~1.5m alongtrack for ATM, other sensors will have a smaller error). Because the error will be partially compensated for by boresight angles depending on flight altitude, the "wrong" numbers should be used anyway unless you recalculate the boresight angles. 17 18 Jan 2008 numbers (Wrong but use anyway): 17 19   Gam  Del  Dst  18 20  ATM  1.2258  0.0051  1.7380  … … 20 22  Hawk  0.9705  0.0049  1.7985  21 23 24 Jan 2008 numbers (Corrected for reference but use "wrong" numbers above): 25   Gam  Del  Dst  26  ATM  0.3450  0.0051  1.7380  27  Eagle  0.4960  0.0036  1.7441  28  Hawk  0.6003  0.0049  1.7985  29 22 30  23 31 2006 obs and results as follows: 24 25 11th Mar. 2008: Note that the email below contains the numbers as originally received, but calculation of the Gamma angle contains an error  "gam = acos( abs(dz) / dst )" should use asin, not acos. Del and Dst are unaffected. Investigation of this suggests this causes an alongtrack error of approx. 1.5m in all 2006/2007 delivered data for ATM, which may be partially corrected by boresight correction (since these numbers were computed using the incorrect leverarm numbers) depending on flight altitude. Other sensors have smaller errors, since the effect of the original calculation error is smaller for the offset angles of these sensors. Correct leverarm numbers are below for reference, new boresight numbers would need to be computed to use these.26 27 Corrected 2006/7 leverarm numbers (use "wrong" numbers below unless you recompute boresight correction)28   Gam  Del  Dst 29  ATM  1.306  0.006353  1.741 30  Casi  1.098  0.007934  1.702 31  Eagle  0.873  0.000781  1.994 32  Hawk  0.806  0.000682  2.117 33 32 34 33 {{{