Phoenix LiDAR Systems User Manual
  • Welcome
  • SpatialExplorer 8 & 9
    • Introduction
    • Installation
      • System Requirements
      • SpatialExplorer-Compatibility
      • Licensing
      • Change Log
    • User Interface
      • Windows
        • AGL Oracle
        • Classify On Selection
        • Coordinate Reference System
        • Corrections
        • Main View
        • Picks
        • Messages
        • Mission Guidance
        • Photo Viewer
        • Project
          • Rover
            • Cameras
              • Camera Acquisition Settings
              • Camera Calibration Settings
              • Camera Processing Settings
              • Camera Tools
                • Load sensor transform/extrinsics from file
                • Calibrate Sensor Manually
                • Edit Receptor Masks
            • IMU
            • GNSS
            • Lidars
              • Lidar Acquisition Settings
              • Lidar Calibration Settings
              • Lidar Processing Settings
              • Lidar Tools
                • Load sensor transform/extrinsics from file
          • Reference Stations
          • Flightplans
          • Geometry
            • Modifying Geometries
          • Grid
          • Ground Control
          • Images
          • Intervals
          • Trajectories
          • Pointclouds
          • Terrains
        • Project Player
        • Sensors
        • SLAM
          • SLAM Processing Profile
        • System Monitor
      • Toolbars
        • File
        • View
        • Selection
          • Cloud Script Tool
        • Workflow
          • NavLab Embedded
            • Processing Options
            • Estimating Primary Antenna Lever Arm
          • Create Intervals
          • Disambiguate Lidar Ranging
          • Create Cloud
          • LiDARSnap
            • Sensor Calibration
            • Trajectory Optimization
              • Aerial Trajectory Optimization
              • Mobile Trajectory Optimization
            • Ground Control with LiDARSnap
              • Vertical Only Adjustment
              • Full Adjustment
            • LiDARSnap Tuning and Parameters
            • Control Point Clouds
            • Example: Optimizing Data from Multiple Scans
          • CameraSnap
            • Auto-detect without review
            • Auto-detect with manual review
            • Manually-Created Matches
            • CameraSnap Reports
          • Colorize Cloud
          • Align to GCPs
            • Adjusting Automatically to GCPs (Vertical Only)
            • Manual Adjustment (Horizontal and Vertical)
          • Reports
          • Export
        • Analytics
          • Classify
            • Classify By Class
            • Classify Noise
            • Classify Statistical Outliers
            • Classify Ground
            • Classify Powerlines
            • Classify Moving Objects
          • Create
            • Create Maps
            • Create Floorplans
            • Create Contours
            • Create Mesh
            • Compute Normals
            • CloudClean
          • Calculate Distance
          • Measure
            • Std. Dev. Along Surface Normal
            • Surface Area and Point Density
            • Volume
          • Compute SOCS
        • LiDARMill
          • Positions
          • Manage Grids
          • View GNSS Antennas
        • Rover
          • Connect to Rover
          • Disconnect from Rover
          • Rover Settings and Profiles
            • Navigation System
            • Sensors
            • Camera Settings
            • LiDAR Settings
          • Shutdown Rover
        • Tools
          • Navigation
            • Plot Trajectories
          • Camera
            • Edit Camera Events
            • Create Camera Sessions from Data
          • Licensing
          • Create Transformation...
    • Workflows
      • Data Processing Workflows
        • Airborne Lidar Processing
        • Mobile Lidar Processing
        • Backpack and Pedestrian Lidar Processing
        • SLAM Lidar Processing
        • LAZ Processing
        • Field Data Check
    • FAQs
  • LiDARMill Cloud
    • Introduction
    • Login/Register
      • User management
    • Quick Start Guide
    • Overview
    • Post Processing Workflow
      • Create New Project
        • Details
        • Project Reference Setup
        • Summary
      • Create New Mission
        • Uploading a SpatialExplorer Mission
        • Uploading a RECON Mission
        • Uploading a Pointcloud Processing Mission
      • Adding Reference Station Data
      • Adding Ground Control Points and Polygons
        • Ground Control Points (GCPs)
        • Polygons
      • Processing Tools
        • NavLab Pipeline
        • Spatial Fuser Pipeline
        • Pointcloud Optimization Pipeline
      • Cloud Viewer
      • Additional Tabs
    • FAQs
  • FlightPlanner
    • Introduction
    • User Interface
      • FlightPlanner Interface Tools
        • Change Theme
        • Feedback, Help, and Changelog
        • Flight Info
        • Delete All
        • Measurement and Reset View
        • Upload Google KMZ file and Delete All KMLs
        • Take off Location
        • Reverse Waypoint Order, Undo, and Auto Update mission flightlines on setting change
        • Address Search
    • Workflow
      • Missions Library
      • Basic UAS LiDAR Mission Planning (FP 9.0)
      • Mission Type
    • Overlap
    • FAQs
  • Hardware and Interfaces
    • Warnings and Safety Notices
      • LiPo Battery Safety
        • General Guidelines and Warnings
        • Pre-Charging Guidelines
        • Charging Process Guidelines
        • Storage/Transportation Guidelines
        • Battery Care Guidelines
      • Laser Safety
        • Class 1 Lasers
        • VUX-240 Laser Safety
      • Aircraft/Rover Operational Safety
    • Connecting and Interfacing with Phoenix Lidar Systems
      • Connect via Rover's Web Interface
      • Connecting via SpatialExplorer
        • Base Station (Notebook) Setup
          • Configure Windows
            • Disable Automatic Updates
            • Change Active Hours
            • Install Latest NVIDIA Drivers
          • Modify Hosts File
          • Wired Ethernet Network Card Setup
          • Install Software Tools
            • 7-Zip
            • Filezilla
            • Teamviewer
            • PuTTY
            • NovAtel Connect and NovAtel Convert4
        • Connect to Rover
          • Connect to Rover as a UDP Client
            • Connect via Wi-Fi
            • Connect via Ethernet
              • Connect via 900 MHz Radio
            • Connect Via Ground-Station-Wi-Fi (Groove)
              • Connect via Ground Station Wi-Fi (Bullet M5)
          • Connect to Rover using a Serial Port
          • Connect to Rover via Connection Service
            • Connect via Cellular
        • User Interface
          • Settings
            • Rover Settings
              • General
              • Navigation System
              • Network
            • Local Settings
          • System Monitor
          • Sensors
          • Satellites
      • Downloading Rover Data
        • Log Files
      • Updating Rover
    • NavBox
      • FLEXPack
        • Specifications
        • Ports and User Elements
        • Status LED
        • Using the CPU button
        • Preparing the System
        • Recording Data
        • Questions & Troubleshooting
      • Air
        • Specifications
        • Ports and User Elements
        • Status LED
        • Using the CPU Button
        • Preparing the System
        • Recording Data
        • Questions & Troubleshooting
      • Scout
        • Specifications
        • Ports and User Elements
        • Using the CPU/Sensor Button
        • Preparing the System
        • Recording Data
        • Questions & Troubleshooting
      • RECON Series
      • Alpha 3
        • Ports and User Elements
        • IMU-32/IMU-33/IMU-34
        • IMU-41/IMU-52
        • IMU-14/IMU-27
    • Camera
      • Sony Mirrorless Cameras
        • Specifications
        • Camera Settings
        • A7R4 Warning Messages
      • A7R4-Lite
        • Sony A7R4-Lite SD card folder setup procedure
      • A6K-Lite Camera
        • Highlights
        • Specifications
        • Warnings
        • Ports and User Elements
        • Status & Activity LED
        • Settings Wheel
        • Mounting
        • Powering ON the Camera - Self-Check
        • Operating with Spatial Explorer
          • Changing the Trigger Interval / Distance
          • Initial Camera Setup
          • Dual A6K-Lite Setup
        • Changing Camera Settings
        • Troubleshooting
      • Ladybug5+ and LadybugCapPro
        • Pre-Procedure
        • Data Acquisition
    • Lidars
      • Real-Time Point Clouds and MTA Disambiguation
    • Inertial Navigation System
      • Orientation and Offsets
        • IMU
        • GNSS Antennas
        • LiDARs and Cameras
      • Wheel Sensor
    • Miscellaneous Hardware
      • Mobile Roof Rack
        • RFM2-Dual LiDAR Mobile Accessory
      • Backpack Lidar Mount
        • Backpack Telescoping Boom
      • Wi-Fi Range Extenders
      • Accessories
        • Cables
          • SMB to SMA GPS Antenna Cable
          • MCX to RP-SMA WiFi Antenna Cable
          • LiDAR / Camera Cable
          • micro USB to USB Type A Female Cable
          • RJ45 Ethernet Cable
          • HDMI Cable Type D to Type A
          • SMA to TNC Ground Mount GNSS Antenna Cable
          • 7.5” Rover GPS Antenna Cable
          • 24” Rover GPS Antenna Cable
        • Power Supply Parts
          • Power Splitter Cable
          • AC Power Supply
          • XT30 3" Extension Cable
          • XT60 Female to XT30 Male Adapter
          • XT60 Male to XT30 Female Adapter
          • XT60 Female to EC5 Male
          • XT60 Extension Cable
        • Antennas
          • Rover GNSS Antenna
          • UHF Rubber Duck Antenna
          • Ground Mount GNSS Antenna
          • Bullet Long Range Module
          • Omni 12dBi Antenna for Bullet Module
          • Rover 5.8 GHz Wi-Fi Antenna RP-SMA
        • Other Components
          • LiDAR/IMU Cable
          • LiDAR Cable
          • IMU Cable
          • AL3 Power Cable with Integrated Splitter
          • EC5 to XT60 Adapter Cable
          • LiPo with EC5 Connector
          • LiPo Charger
          • 5.8 GHz Directional Panel Antenna
          • TNC 90 Degree Adapter
        • Miscellaneous
          • USB Drive
          • USB to Ethernet Adapter
          • Suction Cups w/ Clamps
          • Multi-Tool
          • SMA Wi-Fi Terminator
          • LiDAR Sensor Cover
          • LiPo Guard Battery Bag
          • Cable Accessories Bag
          • Storm Case
          • Foam Divider
  • Data Acquisition and UAV Piloting
    • Flight Planning
      • UAS LiDAR Hot Swapping
    • UAV Data Acquisition
    • Mobile Acquisition
    • Backpack Acquisition
      • Ranger FLEX Initialization and Acquisition Workflow
      • Recon XT Initialization and Acquisition Workflow
    • SLAM Acquisition
    • Navigation System Configuration
      • Navigation System Basics
      • Real-Time and Post-Processing Differences
      • Further Reading
        • GPS Time Status
        • Navigation Procedures
        • IMU Alignment
        • Navigation System Stabilization
    • RECON UAV Acquisition
    • RECON Series Quick Start Guides
      • RECON-XT M300/M350
      • RECON-XT-A FreeFly Astro
      • RECON-A
    • Calibration Flight Strategy
    • Acquisition FAQs
    • Post Acquisition Checks
  • MissionGuidance
    • Introduction
    • Flightplans
    • Heightmaps
    • Setup
    • Operations
  • GNSS Hardware and Ground Control
    • Reference Stations
    • Downloading Reference Station Data
    • Ground Control - Best Practices
    • Stonex S-900 and Cube-A
      • Cube-A project set up
      • Configure base station
        • Configuring Harxon HX-DU8608D radio
      • Configure rover
      • Surveying ground control points
      • Post processing
        • Post processing base station observations
        • Change base coordinates to a post processed position
        • Export points from Cube-A
  • Reports
    • Processing Report
    • Project Report
    • Trajectory Report
  • 3rd Party Software Documentation
    • Bathymetric LiDAR Processing in RiProcess
      • Creating a Project in RiProcess
        • Adding a Navigation Device
        • Adding a Trajectory
        • Adding a Scanner
        • Adding a Camera
        • Adding Control Objects
        • Processing Parameters
          • Exponential Decomposition
          • Page
        • Adding Records
      • Data Processing Wizard
      • Visualize Data
      • RiPrecision
      • RiHydro Workflow
    • RiParameter
    • TerraSolid and Spatix Install
    • Orthomosaic Production with Pix4D
    • InertialExplorer Desktop 8.70 - 8.90 Processing
    • Hyperspectral Data Processing
    • SDCImport Filter Options
      • MTA (Multiple Time Around)
      • Region of Interest
  • Image Processing using PhaseOne IXCapture
  • General FAQ
    • Accuracy Standards & Quantification
      • Precision
      • Relative Accuracy
      • Absolute Accuracy
      • Further Considerations
    • Mapping Terms and Definitions
    • Abbreviations
    • Examples: How to ensure accurate Georeferencing of Trajectories and Pointclouds
      • Example 1: Static Datum
      • Example 2: Dynamic Datum
    • Clock bias adjustment
    • General FAQs
  • Legacy Documentation
    • Offsets, Rotations, and Reference Frames: SpatialExplorer Version 4-7
    • Legacy TerraSolid Documentation
    • Legacy SpatialExplorer Documentation
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On this page
  • IMU Position
  • IMU Orientation
  • External IMUs
  • Internal IMUs
  • Determining IMU Orientations
  1. Hardware and Interfaces
  2. Inertial Navigation System
  3. Orientation and Offsets

IMU

PreviousOrientation and OffsetsNextGNSS Antennas

Last updated 1 year ago

The system’s frame of reference is the IMU (which is why the reference point in the IMU is named the “center of navigation”). All other sensors' (e.g. GNSS antennas, cameras, LiDAR sensors) transforms are specified relative to the IMU's position and orientation.

IMU Position

The position of the IMU center of navigation does not need to be defined. Instead, the position of all other sensors are defined relative to the IMU’s center of navigation.

IMU Orientation

The orientation of the IMU must be defined relative to the vehicle’s orientation. In other words, the IMU orientation defines the direction of the IMU X, Y, and Z axes relative to vehicle-forward, vehicle-right and vehicle-up. Let us first find out how IMU axes are documented.

External IMUs

All Phoenix LiDAR Systems external IMUs include labels indicating the positive direction of all three axes (X, Y, Z) and the location of their origin (also known as the center of navigation of the IMU).

Internal IMUs

Phoenix LiDAR Systems offers the Scout Series mapping solution. Unlike the other mapping solutions offered by Phoenix LiDAR Systems, the Scout features an internal IMU as opposed to external. At the time of writing, the Scout Series supports the IMU-27 and IMU-14.

Instead of an IMU label, the Scout has markings on the outside of the NavBox enclosure indicating the positive direction of the axes and the center of navigation. The positive directions of the Y and Z axes are indicated on the top-right corner on the front of the box and the positive direction of the X axis is indicated on the top-left corner on the side of the box.

In general, the center of navigation of any IMU is always the origin of the X, Y and Z axes as defined on the IMU label or rover-enclosure. For the Scout Series, the X axis center of navigation depends on the type of internal IMU. If your Scout has an IMU-14, the center of navigation for the X axis is the dot located above the IMU-14 marking. If your Scout rover has an IMU-27, the center of navigation for the X axis is the dot located above the IMU-27 marking. Notice the vertical distance offset between the IMU-27 and IMU-14 center of navigation; the IMU-27 center of navigation is a few millimeters above the IMU-14 center of navigation.

Determining IMU Orientations

The difficulty in determining IMU orientations is that imagining a sequence of rotations around a set of axes is simple, but explaining it for others to reproduce exactly is hard. So let us first define some basics:

  • When rotating an IMU around its axes, it is very important in which order that rotation is performed. First rotating e.g. 90 degrees around X, then 90 degrees around Y will result in a different orientation than first rotating the same amounts around Y, then X.

  • When performing rotations around more than one axis, it is important to specify whether the second and third rotations rotate around the initial/fixed axes, or whether they rotate around the rotated axes. The former style is called extrinsic rotation, the latter intrinsic rotation.

  • When rotating around an axis, we always follow the right-hand rule: using your right hand, your thumb points in the direction of the axis you rotate around, and your fingers will curl in the direction of positive rotation. A negative rotation will rotate against the direction of your fingers.

To make this task manageable, our SpatialExplorer desktop software contains a helpful tool, to be found under Tools->Navigation->Convert IMU Orientation:

This dialog allows you to enter the IMU orientation in any convention, either to configure the system, or simply to convert these orientations if that is ever needed in post-processing.

For the majority of times when all IMU axes align with vehicle axes (i.e., no 30-degree rotations for mobile mapping setups), you should use the 3x3 matrix shown in the bottom left. In the dialog shown, the IMU-X axis points vehicle-right, so the top-left field (matching IMU-X/vehicle-right) contains a 1. If IMU-X pointed the opposite way, so, vehicle-left, this field should contain a -1. Continuing with the other IMU axes, since IMU-Y points vehicle-up, the center field contains a 1, and because IMU-Z points towards the vehicle-rear, the bottom-right field contains a 1.

Orientation Example A. IMU-axes X, Y, Z are shown in red, green, blue, respectively. X points vehicle-right, Y points vehicle-up and Z points vehicle-rear. In Inertial-Explorer, this would be X=90, Y=0, Z=0.

Orientation Example B: IMU-axes X, Y, Z are shown in red, green, blue, respectively. X points vehicle-up, Y points vehicle-right and Z points vehicle-forward. In Inertial-Explorer, this would be X=180, Y=90, Z=90.

There are many ways to store and process orientations/rotations in a computer; e.g. matrices, quaternions or euler angles. The dialog shown above will parse the orientation the user enters, transform it into an internal representation and back into the other conventions shown. In that process, it is entirely possible that a user-entered rotation of e.g. X=-90, Y=270, Z=180 becomes X=0, Y=180, Z=-90. This may be very unintuitive for humans, but it still is correct.

Just to make things even more complicated, every navigation system vendor follows a different set of conventions. For example, NovAtel's OEM6 series of navigation systems use a different convention than NovAtel's OEM7 series, and that again differs from NovAtel's Inertial Explorer. To read more about OEM6 and IE, please see document.

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3D view of Scout series orientation
Port side view of Scout series
Side view of Scout series
IMU Orientation dialog showing instant conversions between conventions