Lever arm offset details

This page gives details of the lever arms used when processing data collected from the sensors.

Surveys are undertaken by an external company, usually once a year.

Where possible, the lever arms use precise prime points, e.g. the phase centre of the master (rear) antenna, the centre of the IMU, the scan mirror centre for the LiDAR and the focus point of the lens for the Eagle, Hawk and CASI.

Since 2011, nav data is transformed from the IMU/GPS to an imaginary reference point below the plane (the PAV80). The relevant sensor processing software will then transform from this point to the correct sensor.

Info about calculating the lever arms.


2015

The Twin Otter was surveyed in July 2015. Do not use these values for data collected from the Dornier. At the time of the survey the RCD was broken, so there are no RCD lever arms calculated.

Unless otherwise stated, values are X positive to nose, Y positive to starboard, Z positive down.

IPAS

These values should be entered into IPAS if you are processing the nav for hyperspectral or lidar. They are lever arms from the PAV80 (an imaginary point below the LiDAR instrument) to the device stated:

X Y Z
GNSS (antenna) 4.3533 0.4201 -0.2555
IMU (honeywell) -0.409 0.207 -0.174
IMU (litton) -1.7292 0.1513 -0.1645

The IPAS honeywell is linked with the LiDAR. The IPAS20 (litton) is external and should be used for Fenix processing.

If using the litton IMU the IMU boresight angles also need to be edited and set to 0, 0, 0.

APL

These values go in the file leverarm_values.csv. They are from the PAV80 to the relevant sensor:

X Y Z
Fenix lens -1.7407 -0.0139 1.2605
OWL principal point -0.0685 0.5201 0.35725

2014

Aircraft was surveyed by Sterling Surveys in August 2014

Unless otherwise stated, values are X positive to nose, Y positive to starboard, Z positive down.

IPAS

These values should be entered into IPAS if you are processing the nav for hyperspectral or lidar. They are lever arms from the PAV80 (an imaginary point below the LiDAR instrument) to the device stated:

X Y Z
GNSS (antenna) -0.128 -0.008 -1.674
IMU (honeywell) -0.409 0.207 -0.174

RCD

If you are processing the nav for the RCD, use the following values. They are lever arms from the RCD to the devices stated:

X Y Z
GNSS (antenna) -0.257 -0.066 -1.675
IMU (honeywell) -0.538 0.149 -0.175

If you're using the external IMU (litton, sometimes called IPAS20):

X Y Z
IMU (litton) 0.485 0.145 -0.187

APL

These values go in the file leverarm_values.csv. They are from the PAV80 to the relevant sensor:

X Y Z
Fenix lens 0.477 -0.024 -0.208
OWL principal point 0.881 0.010 -0.226

Aircraft was surveyed by Sterling Surveys in March 2014

Unless otherwise stated, values are X positive to nose, Y positive to starboard, Z positive down.

IPAS

These values should be entered into IPAS if you are processing the nav for hyperspectral or lidar. They are lever arms from the PAV80 (an imaginary point below the LiDAR instrument) to the device stated:

X Y Z
GNSS (antenna) -0.132 -0.014 -1.675
IMU (honeywell) -0.409 0.208 -0.174

RCD

If you are processing the nav for the RCD, use the following values. They are lever arms from the RCD to the devices stated:

X Y Z
GNSS (antenna) -0.261 -0.077 -1.680
IMU (honeywell) -0.538 0.144 -0.179

If you're using the external IMU (litton, sometimes called IPAS20):

X Y Z
IMU (litton) 0.515 0.15 -0.186

APL

These values go in the file leverarm_values.csv. They are from the PAV80 to the Fenix:

X Y Z
Fenix lens 0.504 -0.018 -0.201

2013

Aircraft was surveyed by Sterling Surveys in April 2013

Unless otherwise stated, these values have the PAV80 as the origin and are X positive to nose, Y positive to starboard, Z positive down.

These values are not adjusted for the phase centre of the antenna.

LiDAR

LiDAR lever arm values.

These values should be entered into IPAS:

X Y Z
GNSS (antenna) -0.128 -0.028 -1.679
IMU (honeywell) -0.409 0.207 -0.174

Hyperspectral

Eagle and Hawk lever values. These values go in the file leverarm_values.csv:

X Y Z
Eagle (lens) 0.39 -0.009 -0.198
Hawk (lens) 0.587 0.006 -0.147

RCD

These values have the RCD lens as the origin. They should be entered into IPAS when creating a camera sol file.

X Y Z
GNSS (antenna) -0.260 -0.088 -1.678
IMU (honeywell) -0.541 0.147 -0.173

IPAS 20 (Litton)

If using the IPAS20 (Litton) the following IMU values should be entered into the IPAS software.
Note that the IMU Litton was not in the aircraft at the time of the 2013 survey, values for the GPS to IMU litton from 2012 were used to calculate the values below.

X Y Z
LiDAR IMU (Litton)0.393 0.157 -0.166
RCD IMU (Litton) 0.261 0.097 -0.165

2012

Aircraft was surveyed by Sterling Surveys in July 2012

Full report, images and various workings out are at ~arsf/arsf_data/2012/misc/dornier_survey/

Unless otherwise stated, these values have the PAV80 as the origin and are X positive to nose, Y positive to starboard, Z positive down.

These values are not adjusted for the phase centre of the antenna.

LiDAR

LiDAR lever arm values.

These values should be entered into IPAS:

X Y Z
GNSS (antenna) -0.127 -0.012 -1.677
IMU (honeywell) -0.409 0.207 -0.174

These values go into ALSPP (I think):

X Y Z
Lidar (mirror centre) -0.140 0.000 -0.170

Hyperspectral

Eagle and Hawk lever values. These values go in the file leverarm_values.csv:

X Y Z
Eagle (lens) 0.394 -0.02 -0.143
Hawk (lens) 0.581 -0.019 -0.131

RCD

These values have the RCD lens as the origin. They should be entered into IPAS when creating a camera sol file.

X Y Z
GNSS (antenna) -0.258 -0.074 -1.678
IMU (honeywell) -0.540 0.145 -0.175

2011

Aircraft was surveyed by Sterling Surveys in March 2011.

LiDAR

The LiDAR measurements are made from the antenna to a reference point, then transformed from that reference point to an internal point (PAV 80). The reference point is the front left corner of the LIDAR sensor unit casing.

Measured antenna to reference point numbers:

  • X = 0.173 ; Y = 0.073 ; Z = -1.412

LiDAR lever arm values (and the values to enter into the software):

X Y Z
GNSS -0.144 -0.029 -1.672
IMU -0.411 0.206 -0.192
User Frame -0.142 -0.001 -0.188

These values are entered in the flight planning software and should automatically populate in IPAS.

Hyperspectral sensors

The hyperspectral measurements are made from the antenna to a reference point, then transformed from that reference point to the Eagle/Hawk lens. The reference point is the forward port corner of the Eagle/Hawk base plate.

Measured antenna to reference point numbers:

  • X = 0.864 ; Y = 0.300 ; Z = 1.569

Eagle and Hawk lever arm values are:

X Y Z
Eagle 0.559 -0.015 -1.543
Hawk 0.729 -0.015 -1.543

RCD

For processing the sol file for the RCD use the following lever arm values:

X Y Z
GNSS -0.256 -0.090 -1.612
IMU -0.523 0.145 -0.132

2010

Where unspecified, the measurements are as in the previous year.

LIDAR

Internal measurements provided by Leica:

  • PAV80 rotation point to RCD lens (no spacer): X= 0.112 ; Y = 0.061 ; Z = -0.060

Axes are:

  • X = increasing towards the front of the plane
  • Y = increasing to port
  • Z = increasing downwards

Note that to get to PAV80 from reference point we apply: X = -0.14 ; Y = 0 ; Z = -0.17 (see email March 2010 from Leica)

Lever arm values to enter into the IPAS software for 2010:

X Y Z
GNSS 0.019 -0.024 -1.692
IMU -0.411 0.206 -0.192
User Frame -0.142 -0.001 -0.188

These values are entered in the flight planning software and should automatically populate in IPAS.

Hyperspectral sensors

We're told these are the same as end of 2008. Note: These are xyz co-ords, not gam-del-dst

X Y Z
Eagle 0.408 0.001 -1.548
Hawk 0.578 0.001 -1.548

2009

Hyperspectral sensors

We're told these are the same as end of 2008. Note: These are xyz co-ords, not gam-del-dst

X Y Z
Eagle 0.408 0.001 -1.548
Hawk 0.578 0.001 -1.548

TABI

Measured by ARSF-Ops relative to Hawk (numbers converted below to relative to the GPS antenna), not surveyed. Should be accurate enough though.

X Y Z
0.858 0.001 -1.548

Applanix IMU

Use 2006/7 numbers?

Leica LIDAR + IMU

The LIDAR survey measurements are made from the antenna to a reference point, then transformed from that reference point to internal points (the IMU and mirror center). The reference point is the front left corner of the LIDAR sensor unit casing. Survey was in late 2008.

Measured antenna to reference point numbers:

  • X = 0.010 ; Y = 0.078 ; Z = -1.432

Internal measurements provided by Leica:

  • reference point to mirror center: X = 0.169 ; Y = 0.102 ; Z = 0.090
  • reference point to IMU: X = -0.269 ; Y = 0.207 ; Z = -0.004
  • laser mirror centre to RCD lens (no spacer): X= 0.239 ; Y = 0.062 ; Z = -0.060

Axes are:

  • X = increasing towards the front of the plane
  • Y = increasing to port
  • Z = increasing upwards

2008

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 along-track 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 re-calculate the boresight angles.

Jan 2008 numbers (Wrong but use anyway, or we have to redo boresights):

Gam Del Dst
ATM 1.2258 0.0051 1.7380
Eagle 1.0748 -0.0036 1.7441
Hawk 0.9705 -0.0049 1.7985

Jan 2008 numbers (Corrected for reference but use "wrong" numbers above, unless you've redone boresights):

Gam Del Dst
ATM 0.3450 0.0051 1.7380
Eagle 0.4960 -0.0036 1.7441
Hawk 0.6003 -0.0049 1.7985

VOCALS

Use these numbers for VOCALS flights from autumn 2008. Note: These are xyz co-ords, not gam-del-dst (ie use -acx, not -acv)

X Y Z
Eagle 0.2302 0.001 -1.548
Hawk 0.4002 0.001 -1.548

Applanix IMU

Use 2006/7 numbers?

Leica LIDAR + IMU

The LIDAR survey measurements are made from the antenna to a reference point, then transformed from that reference point to internal points (the IMU and mirror center). The reference point is the front left corner of the LIDAR sensor unit casing. Survey was in late 2008.

Measured antenna to reference point numbers:

  • X = 0.010 ; Y = 0.078 ; Z = -1.522

Internal measurements provided by Leica:

  • reference point to mirror center: X = 0.169 ; Y = 0.102 ; Z = 0.090
  • reference point to IMU: X = -0.269 ; Y = 0.207 ; Z = -0.004

Axes are:

  • X = increasing towards the front of the plane
  • Y = increasing to port
  • Z = increasing upwards

The GNSS lever arms to enter into the IPAS software are (i think): X = 0.159 Y = -0.024 Z = -1.522

The IMU lever arms to enter into the IPAS software are: X = -0.269 Y = 0.207 Z = -0.004


2007

Use 2006 numbers..


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

==========================================================================================

Applanix IMU Lever arm offsets

Year X Y Z
2006 1.068 0.182 1.489
2007 Use 2006 :S Use 2006 :S Use 2006 :S

N.B. Some of the 2006, 2007 data has a preset IMU lever arm offset of 0.907, 0.190, 1.783 - not sure where this comes from, perhaps coords noted on the plane? Dave Davis has said to use the 1.068, 0.182, 1.489 offsets.

Last modified 17 months ago Last modified on Jul 5, 2017 12:29:23 PM