Changes between Initial Version and Version 1 of Processing/LeverArmOffset

Timestamp:

Jan 29, 2008, 2:17:28 PM (17 years ago)

Author:

benj

Comment:

Created

Processing/LeverArmOffset

@@ +1 @@
+== Lever arm offset details ==
+
+This page gives details of how the lever arm offset is calculated.
+
+All nav is transformed back to the master antenna on the rear of the cabin roof, and then [wiki:Processing/Flow/aznav aznav] transforms nav from there to each sensor as required when the individual sensor data is processed. AT4 nav is already wrt this antenna, and the IMU data is transformed back to the antenna during Applanix processing.
+
+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.
+
+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.
+
+Initially it is necessary to make sure you have the correct sensor prime point coords as observed.
+
+Then aznav sorts out what axis system has been used by the surveyors and swaps the cooridnates around until it gets it in the NASA Standard Aircraft system  [ Y+ port, X+ tail to nose, Z+ up ]. Then do the angle calcs. 
+
+----
+
+2006 obs and results as follows:
+
+{{{
+v:200601 may 2006
+
+2006 D-CALM instrument coords  from SJR 9th May
+------------------------------------------------------------------------------------------
+
+        z       x        y       Z offset  X offset  Y offset   dst      gam      del
+
+ATM    8.991  96.9065  99.9881  -1.68    0.4565   -0.0029      1.741  0.2655  0.006353
+CASI   9.156  97.22509 99.98485 -1.515   0.775092 -0.00615     1.702  0.4732  0.007934
+Eagle  9.143  97.7307  99.99    -1.528   1.2807   -0.001       1.994  0.6977  0.000781
+Hawk   9.143  97.9155  99.99    -1.528   1.4655   -0.001       2.117  0.7644  0.000682
+IMU    9.182  97.5181  99.8089  -1.489   1.0681   -0.1821      1.841  0.6287  0.1689
+
+560                             -1.476   1.4831   -0.0061      2.092  0.8264  0.004113
+
+Pant  10.945 100.001   95.095    0.274   3.551    -4.815
+Sant  10.906 100.000  104.91     0.235   3.550     5.000
+Fant  10.843 101.661   99.989    0.172   5.211     0.079
+
+------------------------------------------------------------------------------------------
+Aant   10.671 96.450  99.991     0.0     0.0       0.0
+
+------------------------------------------------------------------------------------------
+
+Axes:  Y+ port,  X+ tail to nose, Z+ up
+Antennas:  name, postion, AT4 name, survey name
+Aant = aft  = master  = GPS4
+Fant = fore = slave_1 = GPS3
+Pant = port = slave_2 = GPS1
+Sant = starboard = slave_3 = GPS2
+--------------
+Sensor offset vector paras allowing for this coordinate system
+
+dx == X offset, dy = Y offset, dz = Z offset
+
+dst = sqrt( dx * dx + dy + dy + dz + dz ) 
+
+gam = acos( abs(dz) / dst )
+
+del = atan( dy / (-dx) )
+
+Units:  dst: metres,  gam, del: radians
+
+-----------------
+Verification test
+
+p = r = h = 0
+ant1:  lat: 52.0 lng: -3 hgt: 1000
+
+IMU is at:  lat: 52.00000959  lng: -2.99999734  hgt: 998.511013
+
+==========================================================================================
+}}}