UgCS for drone-based LIDAR missions

The UgCS toolset for LIDAR mission planning currently is enabled for UgCS ENTERPRISE license and for supported DJI drones. To use the LIDAR toolset - create a new route for DJI M600, M300 or M210/M200.
 

Overview

LIDAR (Light Detection and Ranging) is gaining popularity with professional drone surveyors. However, to get accurate LIDAR scan results, a pilot needs to follow a few rules:

• Initialize IMU properly
• Maintain correct flight height and line spacing between scans to ensure coverage and point density
• Ensure the right drone turns and line scanning to minimize IMU error accumulation and excessive shaking of LIDAR above the area of interest

Making everything right is impossible in a manual flight mode and extremely hard with flight planning tools tailored for photogrammetry surveys. UgCS LIDAR toolset by SPH Engineering unlocks the full potential of LIDARs making remote sensing most effective with no human errors:

• IMU initialization patterns as drone commands:
  • Eight figure
  • U-figure
• Flight patterns for route planning:
  • LIDAR Area
  • LIDAR Corridor
• The preset drone turns:
  • Bank turns
  • Loop turns
• AGL (above ground level) and AMSL (above mean sea level) line spacing

Let’s see in more detail how all these things work.

Contents

• IMU Initialization
  • Eight figure
  • U-figure
• Flight planning techniques
  • Scanning the area of interest
  • Scanning the corridor
  • Common input parameters
  • Field of view and line spacing
  • Turns
  • Area buffer and overshoot
• Supported LIDARS

IMU Initialization

IMU initialization is typically performed at least two times per flight. Before scanning begins and after scanning ends. Optionally, the pilot may pause the flight and make additional IMU initialization to reset accumulated errors. This is why we implemented this function as a drone command so that the pilot may run it at any time. For this command to run, the drone should already be in the air.

Different LIDAR manufacturers recommend various patterns. In UgCS, we support the two most popular: eight figure and U-figure.

   

Eight figure

The main goal of the calibration pattern is to put drones to their maximum capacity in terms of roll angle. That literally means that a pilot wants to pass the eight figure at the maximum possible speed, which will make a proper IMU calibration.

To add the figure, a pilot clicks on the map to specify a center and an altitude and then the width, length, speed, altitude, and direction angle of the turns.

   

U-figure

Figure 1. U-figure turn

Input parameters are very similar to eight-figure. However, the generated trajectory is different. The drone makes several passes back and forth and then makes a U-turn (Figure 1).

To add the figure, a pilot clicks on the map to specify a center and an altitude and then the width, length, speed, altitude, and direction angle of the turns.

   

Flight planning techniques

LIDAR survey typically employs the following patterns:

• Corridor
• Area

Drones can be equipped with either LIDAR or LIDAR and a Photo Camera. In the latter case, we must consider the FOV of the LIDAR and the FOV of the camera and choose the smallest one.

Scanning the area of interest

LIDAR area scanning is helpful for the following: construction sites, open-pit mines, power stations, landfills, archeology, and forestry.

   

The pilot has to specify the following:

• Area boundaries as a polygon
• Flight height AGL or AMSL
• Effective scanner FOV (field of view)

The area can be divided into the following trajectories:

• Single grid
• Double grid

Scanning the corridor

LIDAR corridor scanning is helpful for the following: roads, power lines, and pipelines.

   

The corridor can be divided into the following trajectories:

• Singlepass - along the corridor center line
• Multipass to cover a certain corridor width with scans of a certain lateral overlap

In the case of corridor geometry, a user specifies a centerline and width.

Common input parameters

Besides the general trajectory shape, pilots input the following:

   

Field of view and line spacing

The pilot always specifies FOV manually. The general assumption is that a drone always flies at altitudes lower than the LIDAR range; i.e. the pilot defines FOV and altitude independently. These parameters affect line spacing.

Line spacing is calculated differently for AGL and AMSL modes:

Figure 2a. Line spacing calculation for AGL
 

Figure 2b. Line spacing calculation for AMSL

SW (Scan Width) = 2*H*tan (FOV/2)

Line Spacing (Side distance) = SW*(1-Side Overlap Percentage)

   

Turns

The quality of LIDAR data is greatly influenced by the way drone makes turns. The most important thing is to reduce the shaking of the sensor and follow the trajectory as accurately as possible.

The turn should look like a normal bank turn for angles bigger than “Loop turn angle” degrees (Figure 3).

Figure 3. The trajectory of the turn

The radius of the bank turn should be as specified in the “Bank turn radius.”

For angles less than or equal to “Loop turn angle” degrees, turns may look like a loop maneuver (Figure 4).

Figure 4. The trajectory of the loop turns

Important: after the loop turn, before entering the next segment, the drone should fly “Straight flight time after turn” seconds straight.

Loop turns do not apply to turns in overshoot segments. In case of overshoot turns, a bank pattern applies.

Area buffer and overshoot

By default, trajectory and LIDAR footprint are assumed to be inside the corridor or area.

An area buffer applies to all flight areas to improve coverage on borders by extending the original shape.

Overshoot extends forward passes to make turns outside of the main trajectory.

 

Overshoot = 0 Area buffer = 0
Overshoot > 0 Area buffer = 0
Overshoot = 0 Area buffer > 0
Overshoot > 0 Area buffer > 0

 

Supported LIDARS

• DJI

• YellowScan

• Phoenix LIDAR

• Riegl

• LIDAR USA

• GeoCue

• Rock Robotics

• GeoSun LIDAR

UgCS LIDAR toolset is currently supported for DJI M300, M600, M210/200 drones.

 

The new LIDAR functionality is available on the UgCS ENTERPRISE license type.
 

Try UgCS ENTERPRISE for free

Useful links

• UgCS Support Team
• UgCS Manuals and Documentation