True View Lever Arm Offset Override

Some scenarios may require you to process your True View data with different lever arm offsets or IMU mounting angles than the ones recorded in the APX-15 at the time of acquisition. For instance, if you move the system to a new drone, but forget to update the lever arm values following the applicable system hardware users guide before collecting data. The steps below explain how to use a lever arm offset override to process your data in EVO with different lever arm offsets. Applies to True View EVO v2021.1.17.0 and later.

Step 1 – Import your cycle into True View EVO.

Step 2 – In Windows File Explorer, navigate to the system folder inside your EVO project folder (Area_ /Cycle_/System_), or a folder of your choosing.

Step 3 – Create a json file named GNSSLeverArmOverride.json that defines one or both of these 3-tuples to define the lever arm offset override:

{   "IMUMountingAngles": {   "Override": "false",   "RefToIMUMountingAnglX": "0.0",   "RefToIMUMountingAnglY": "0.0",   "RefToIMUMountingAnglZ": "0.0"   },   "LeverArm": {   "Override": "false",   "PriGNSSLeverX": "0.0",   "PriGNSSLeverY": "0.0",   "PriGNSSLeverZ": "0.0"    }   } 

Or, use these 3-tuples for the True View 620 or 640:

{   "IMUMountingAngles": {   "Override": "false",   "RefToRemoteIMUMountingAnglX": "0.0",   "RefToRemoteIMUMountingAnglY": "0.0",   "RefToRemoteIMUMountingAnglZ": "0.0"   },   "LeverArm": {   "Override": "false",   "PriGNSSLeverX": "0.0",   "PriGNSSLeverY": "0.0",   "PriGNSSLeverZ": "0.0"    }   } 

Being sure to set the override to “true” for the desired section(s).

Step 4 – Enter the desired lever arm offsets and/or mounting angles. Save and close the GNSSLeverArmOverride.json file.

Step 5 – In EVO, select the POSPac Processing Wizard and on the Input Settings Page, browse to a JSON file that defines one or both of the 3-tuples above to override the APX values when processing. Configure the remaining as normal.

Showing the POSPac Processing Wizard -Input Settings Page: Select Override APX Mounting Parameters JSON File section
True View EVO: POSPac Processing Wizard -Input Settings Page: Select Override APX Mounting Parameters JSON File

Step 6 – Confirm the correct offsets were used by examining the GNSS-Inertial Processor Configuration section of POSPac report.

GNSS-Inertial Processor Configuration with highlight on the GNSS lever arm parameters used for processing
POSPac Report with highlight on the GNSS lever arm parameters used for processing

Step 7 – Execute the remaining processing steps as normal. Be sure to re-create the True View Trajectories and subsequent steps if they were previously created with incorrect lever arms used in the POSPac processing.

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