Changes between Initial Version and Version 1 of Processing/LeverArmOffset


Ignore:
Timestamp:
Jan 29, 2008 2:17:28 PM (12 years ago)
Author:
benj
Comment:

Created

Legend:

Unmodified
Added
Removed
Modified
  • Processing/LeverArmOffset

    v1 v1  
     1== Lever arm offset details ==
     2
     3This page gives details of how the lever arm offset is calculated.
     4
     5All 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.
     6
     7The 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
     9The 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.
     10
     11Initially it is necessary to make sure you have the correct sensor prime point coords as observed.
     12
     13Then 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.
     14
     15----
     16
     172006 obs and results as follows:
     18
     19{{{
     20v:200601 may 2006
     21
     222006 D-CALM instrument coords  from SJR 9th May
     23------------------------------------------------------------------------------------------
     24
     25        z       x        y       Z offset  X offset  Y offset   dst      gam      del
     26
     27ATM    8.991  96.9065  99.9881  -1.68    0.4565   -0.0029      1.741  0.2655  0.006353
     28CASI   9.156  97.22509 99.98485 -1.515   0.775092 -0.00615     1.702  0.4732  0.007934
     29Eagle  9.143  97.7307  99.99    -1.528   1.2807   -0.001       1.994  0.6977  0.000781
     30Hawk   9.143  97.9155  99.99    -1.528   1.4655   -0.001       2.117  0.7644  0.000682
     31IMU    9.182  97.5181  99.8089  -1.489   1.0681   -0.1821      1.841  0.6287  0.1689
     32
     33560                             -1.476   1.4831   -0.0061      2.092  0.8264  0.004113
     34
     35Pant  10.945 100.001   95.095    0.274   3.551    -4.815
     36Sant  10.906 100.000  104.91     0.235   3.550     5.000
     37Fant  10.843 101.661   99.989    0.172   5.211     0.079
     38
     39------------------------------------------------------------------------------------------
     40Aant   10.671 96.450  99.991     0.0     0.0       0.0
     41
     42------------------------------------------------------------------------------------------
     43
     44Axes:  Y+ port,  X+ tail to nose, Z+ up
     45Antennas:  name, postion, AT4 name, survey name
     46Aant = aft  = master  = GPS4
     47Fant = fore = slave_1 = GPS3
     48Pant = port = slave_2 = GPS1
     49Sant = starboard = slave_3 = GPS2
     50--------------
     51Sensor offset vector paras allowing for this coordinate system
     52
     53dx == X offset, dy = Y offset, dz = Z offset
     54
     55dst = sqrt( dx * dx + dy + dy + dz + dz )
     56
     57gam = acos( abs(dz) / dst )
     58
     59del = atan( dy / (-dx) )
     60
     61Units:  dst: metres,  gam, del: radians
     62
     63-----------------
     64Verification test
     65
     66p = r = h = 0
     67ant1:  lat: 52.0 lng: -3 hgt: 1000
     68
     69IMU is at:  lat: 52.00000959  lng: -2.99999734  hgt: 998.511013
     70
     71==========================================================================================
     72}}}