NEXUS 800 Powered by HYPACKTAKE AERIAL SURVEYING AND MAPPING TO THE NEXT LEVEL WITH THE NEXUS

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HAROLD ORLINSKY

NEXUS-800 : A complete Solution

PLANNING

• Project Creation• Sensor

Integration

ACQUISITION

• Real Time View• Targeting• Data Logging

POST PROCESSING

• Data Editing• Smart Filters• Point Cloud &

Imagery Analysis

DATA ANALYSIS

• Surface Comparison

• Volumetrics• Contouring

PRODUCT CREATION

• XYZ, LAS, PTS• DXF, KMZ,

WebGL, STL• Contours, TIN

The NEXUS-800 ships with the latest versions of the HYPACK and HYSWEEP software for both data collection and processing.

NEXUS-800 UAV Specifications

• Heavy Lifter ~8 lbs. (3.7 kg)

• Auto Takeoff/Landing

• 10 – 15 minute flight time (12 min avg)

• Hot swappable power (no shut down required)

• Area coverage example: 200 x 200 meter area (40,000 square

meters) covered in 5 minutes at 4 m/s and a 40 meter altitude.

Photogrammetry v.s. LiDAR Survey

Source http://flight-evolved.com/lidar-vs-photogrammetry/#

“Photogrammetry can only create points based on what the sensor of the camera can detect illuminated by ambient light. This problem is compounded by commonly used small imaging sensors with poor sensitivity. As a result, flights over vegetated areas, with limited ground visibility and deep shadows, produce few ground points and only treetops are accurately represented.”

Lets Meet the NEXUS and the Sensors

SBG Ellipse2-D Antennas

Velodyne VLP-16 Puck

Canon DSLR

SBG Ellipse2-DMounted behind the Velodyne

LiDAR Sensor on the NEXUS-800

Laser: Mechanical/ Electrical/ Operational

Output:• Time of Flight Distance Measurement with Calibrated Reflectivity• 16 Channels• Measurement Range: Up to 100 m• Accuracy: ±3 cm (Typical)• Single and Dual Returns (Strongest, Last)• Field of View (Vertical): +15.0° to -15.0° (30°)• Angular Resolution (Vertical): 2.0°• Field of View (Horizontal): 360°• Angular Resolution (Horizontal/Azimuth): 0.1° – 0.4°• Rotation Rate: 5 Hz – 20 Hz• Power Consumption: 8 W (Typical)• Laser Product Classification: Class 1 Eye-safe per IEC 60825-1:2007 & 2014• Wavelength: 903 nm• Beam Size @ Screen: 12.7 mm (Horizontal) x 9.5 mm (Vertical)• Beam Divergence Horizontal: 0.18° (3.0 mrad); Vertical: 0.07° (1.2 mrad)

Velodyne Channels

The VLP-16 offers a full compliment of lasers that can be enabled or disabled to suit the requirements of the survey.

VLP-16 Range Filter

With this Filter, you can apply a Minimum (‘Min’) and/or a Maximum (‘Max’) Range Distance.The ‘Min’ Range Distance can be very useful when the laser is mounted on the top of the vessel and you want to instantly ignore the Beams that are striking the vessel, from being recorded within the data file.

NOTE: Only Beams that are being returned within the GREEN area will be recorded in the raw data file.The VLP-16 has Returns of up to 100 meters(useful range depends on application)

VLP-16 Angle Filter

Angle FilterThe Angle Filter sets the ‘Field of View’ for the laser and works in ‘reverse’ of what you would normally expect a Filter to do. With the Angle Filter, you enter the values in which you ‘want to keep’, instead of ‘want to remove’.

In this example, the Angle filter will ‘Start’ at the ‘Min’ angle of 45o

continue to the ‘End’ at the ‘Max’ angle of 315o and ‘keep’ ONLY the data points that fall within those Field of View angles.

This example is also assuming that the laser is mounted in the ‘Vertical’ orientation.

Ellipse2-D: Miniature Dual GNSS INS

0.1° Roll and Pitch over 360°0.2° Heading (Dual Antenna GNSS)5 cm Real-time Heave, adjusted to the wave period2 cm RTK GNSS Position (option)

Key Features:Very Low Noise Gyroscopes, High Quality AccelerometersSurvey-Grade L1/L2 GNSS ReceiverDifferential Corrections (RTCM)200 Hz Output Rate – Typically collected at 50 Hz2 years warranty

Conducting a Survey

HYPACK SURVEY – HYSWEEP SURVEY

Real Time Cloud

Real Time Cloud allows the user to see the data as it is recorded.

The data in the Real Time Cloud is both motion and tide corrected.

Expected Accuracies

Understanding the potential errors in LiDAR data

Material ReflectivitySnow 80% White Concrete 78% Bare Aluminum 74% Vegetation 50% Bare Soil 30% Wood Shingle 17% Water 5% Black Asphalt 3%

The source used here is designed to show the reflectivity of material using Solar Radiation.

This table shows the reflectivity of various common materials. For example, snow reflects 80% of the light that falls on it, which means that it absorbs 20%. This also means that if there is 100 watts of light energy falling on the snow, 80 watts will be reflected and 20 watts will be absorbed.

The test site at the HYPACK office has coverage with Black Asphalt, Water, Vegetation and Bare Soil.

20 Meter Flight Profile – Low Vegetation

Area of low vegetation – 20 meters The images below show an area of low vegetation, freshly planted grass and bare soil. The average vertical uncertainty in this area measures out to +/- 5cm. This area was chosen as a low to moderate area of reflectivity with good returns.

20 Meter Flight Profile – Black Asphalt

Area of Black Asphalt – 20 MetersThe images below show an area of black asphalt. Based upon the reflectivity profile the area should have a very low reflective surface. The measurement of uncertainty is ~12cm ( +/- 6cm ).

35 Meter Flight Profile – Low Vegetation

Area of low vegetation – 35 meters The images below show an area of low vegetation, freshly planted grass and bare soil. The average vertical uncertainty in this area measures out to 8-10 cm ( +/- 5cm ). This area was chosen as a low to moderate area of reflectivity with good returns.

Flight Controller ¥ Autonomy Module

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• DJI Industrial Flight Controller

• Flight Planning occurs through using DJI’s Ground Station App (iOS only)

• DJI Ground Station provides full autonomy to NEXUS Auto Take Off Auto Landing Return to Home

The data collected in that hour – 5 Acres

At the end of the survey, prior to leaving the site, the data is opened in MBMAX 64 to ensure the data collected was sufficient for final products prior to departing the project site.

A site survey of the Umstead Site

2,249,000 XYZ Data Points

A single flight of 5 minutes. Speed was

Processing the SURVEY

Processing tools within HYPACK

The NEXUS-800 uses the standard HYPACK and HYSWEEP programs for processing the survey to allow users familiar with the software to quickly adapt to the NEXUS-800 survey data.

Data Splitter – Break the survey into lines

The Data Splitter program allows the flight to be broken into segments. When the flight is broken into segments, any errors induced in the turns are avoided as well as allowing the Patch Test tools to be used to verify the calibration.

Data Splitter & Merge Editor

Once the files are loaded the data is split using the cursor. Left click on the area display to create a border for splitting. The Red Circles denote the beginning of the line and the Green Circles the end. Double clicking on the Red Circle deletes that selection. Each circle can be dragged around the survey to extend or shorten a segment.

Flight Time at the NCDOT Test Site

Start Time: 15:55.52

End Time: 15:59.00

Total Flight Time: 5 minutes 6 seconds

Typical Settings and Filters for LiDAR data

The LiDAR data is generally clean of the spikes experienced in a Multi Beam Sonar survey.

The data can be cleaned with a series of filters. The SBG code for Narrow Lane RTK, the mode required for good data, is 7.

Using the Manual Selection Tool

The Manual Selection Tool in the MBMAX Editor allows the user the ability to create a profile for viewing/editing at any location within the data.

Flight Sensor Data

The Tide window allows the user to check the flight data for proper elevation.

The Pitch and Roll window allows the user to view and edit the data from the IMU if necessary.

The Speed window allows the user the ability to QC the flight speed. If the speed is edited, the corresponding position is deleted and the LiDAR data that goes along with it as well.

Vegetation Filter

The Vegetation Filter used in the Profile Window attempts to differentiate between the ground level and any vegetation that may be growing there.

The filter analyzes in the profile segment looking for the minimum elevation in each segment. This elevation is then interpreted as the ground level.

There are three parts to the Vegetation Filter that can be adjusted.

Window Size: The along profile segment distanceOverlap Percent: The amount each window overlaps with the previous segmentGate Size: In elevation units, the distance above and below the interpreted ground the filter will allow data to be retained. A tight filter will eliminate more data but could remove valid returns.

In this example of the Vegetation Filter the Window Size is too small to effectively remove the vegetation from the display.

In the second image the Window Size is good but the Gate is eliminating some good data.

Vegetation Filter

The final result of the filtered data has removed a portion of or in some cases the entire building. Saving this out to XYZ will allow for the ground elevations to be observed and utilized where available. Separate processing can be accomplished to export the building XYZ data if that is of interest as well.

The Profile Window has the ability to filter the data in the display and also has the ability to filter the entire survey. In the image below the data was filtered just in this profile. The profiles are stacked to allow multiple profiles to be visible in the in the window.

Vegetation Filter Results

In this image the display shows areas as green where the count of returns per square foot is greater than 2. The red areas are displayed were there are less than 2 returns per square foot. Areas under the tree cover, where the Vegetation Filter did most of the work, contain a significant amount of returns.

Final Products for LiDAR Data

Final Products from LiDAR Data

Portable Web Point Cloud Format

LiDAR Point Cloud Colored by RGB Satellite Image

AutoCAD DXF Contours

3D Mesh - Poisson Reconstruction

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3d Mesh Rendering can be accomplished with the 3D MESH program in HYPACK.

Hammonasset Beach Survey

This survey was completed using all 16 channels of the Velodyne Puck.

Thank you!