Eagleeye LiDAR Mapping System

LiDAR (Light Detection And Ranging) is a rapidly growing and increasingly accepted technology in the aerial mapping industry. This technology utilizes airborne lasers to measure distance between the laser scanner and the ground and/or objects on the ground. With this technology, a laser scanner “paints” surfaces below with millions of laser points and measures the time of the “bounce back” to determine distance from the aircraft to the ground or the object. This measurement when combined with precise data about the location and orientation of the aircraft provides a “point cloud” which yields an excellent model of the area being mapped.

Based upon many years experience with LiDAR, Tuck developed the eagleeye mapping system®  which is a fully integrated helicopter-based aerial mapping system that simultaneously obtains LiDAR and digital photography. This helicopter-based system is specifically designed for low altitude mapping where extreme accuracy is required for engineering design along with high-resolution digital photography for orthophotography production.

Accuracy is the feature hallmark of eagleeye mapping system® . This system can obtain vertical accuracy as precise as 1/2″- 2″ and has the flexibility to obtain lesser accuracy levels to match client needs. Tuck has two (2) helicopters and one aircraft equipped with the proprietary eagleeye mapping system®. The two helicopters are the Bell JetRanger BIII, the Bell LongRanger LIII, and the aircraft is a Cessna 206.

PROJECT APPLICATIONS
The eagleeye mapping systems® are normally used for projects with accuracy requirements that are better than one foot (1’). The helicopter-based systems acquire data quickly and operate in a cost-effective mode. Typical projects include:

  • Transmission line and utility corridors
  • Highway design
  • Site design
  • Airport mapping including obstruction surveys
  • Bridge and stream surveys
  • Volume calculations
  • Railroad mapping
  • Water and sewer design mapping
  • Surface mine pit maps
  • High-detail city mapping

SYSTEM CONFIGURATION
The eagleeye mapping system® includes a high frequency Riegl laser, a high-resolution Leica RCD30 metric digital camera, dual frequency GPS and 200 Hz Inertial Measurement Unit (IMU). The IMU, laser, and digital camera are integrated via proprietary software and mounted together to ensure accuracy and reliability.

Digital Camera : The system includes the Leica RCD30 precision digital camera with custom optics and advanced position/orientation technology specifically designed for airborne applications. The Leica camera obtains 1.5” pixel resolution at 500 feet AGL.

Tuck Mapping Digital CamerasLeica LCD Digital Camera

Tuck Mapping Digital CamerasLeica LCD Digital Camera

Array: 8956 (Cross Track) X 6708 (Along Track)
Pixel Size: 0.006 mm
Filter Array: Leica NAG-D 50mm
Light Metering: Center weighted average
Shutter Speed: 125-400
Bands: Red Green Blue                IR
Range (nm): 400-500 500-600 600-680     780-880
Imagery Resolution: 14-bit
Orientation: Direct geo-referencing with IMU

Riegl VQ-480 Laser Specifications

pob0111_prod08_VQ-480Laser pulse rate: 300,000 Hz
Flight altitude: 500-1000 ft. Above Ground Level (AGL)
Swath width: 300-1000 ft. (function of flying height)
Laser wave length: 1550 µm
Scan angle: +/- 30 degrees (60 degree swath)
Beam divergence: 0.3 mrads
Intensity: 16-bit GeoTIFF intensity imagery
Point Density: Typically 40 to 60 points per square meter

Scanning Mechanism: rotation polygon mirror

Scan Pattern: parallel scan lines
Riegl LMS-Q560 60 Laser


Laser pulse rate: 240,000 Hz
Flight altitude: 300-3000 ft. Above Ground Level (AGL)
Swath width: 300-3000 ft. (function of flying height)
Laser wavelength: 1064 µm
Scan angle: +/- 30 degrees (60 degree swath)
Beam divergence: < 0.5 mrads
Intensity: 8-bit GeoTIFF intensity imagery
Point Density: Typically 40 to 60 points per square meter

Scanning Mechanism: rotation polygon mirror

Scan Pattern: parallel scan lines

Riegl 680 Laser Specification

appl2Laser pulse rate: 400,000 Hz
Flight altitude: 500-5000 ft. Above Ground Level (AGL)
Swath width: 500-5000 ft. (function of flying height)
Laser wavelength: m
Scan angle: +/- 30 degrees (60 degree swath)
Beam divergence: < 0.5 mrads
Intensity: 16-bit GeoTIFF intensity imagery
Point Density: Typically 40 to 60 points per square meter

Scanning Mechanism: rotation polygon mirror

Scan Pattern: parallel scan lines

Orientation Technology:

An onboard Trimble GPS dual frequency receiver ensures precise positional accuracy for eagleeye by collecting and providing data up to 1/10 second epoch.

The Inertial Measurement Unit (IMU) is an Applanix 200 Hz POS AVV5 Model 410 system that collects orientation data 200 times per second to provide precise location of the sensors at the time of data acquisition. The positional accuracy of the unit is .05-.3 meters: angular accuracy is 0.008 degrees in pitch and roll and 0.015 degrees in heading: velocity accuracy is 0.005 m/s.

GPS base stations collect data on the ground to ensure processing accuracy. These base stations are positioned on or near the project approximately ten miles from helicopter flight lines to ensure accuracy of the processed trajectory. The small number of GPS base stations required and flexibility of their location allow fast data collection, lower cost and minimal safety risk to on-ground personnel while maintaining exceptional accuracy.

The GPS antenna is an aviation grade micro strip model GPS 512 manufactured by AeroAntenna Technology, Inc. The LNA gain on the antenna is 26 dB +/- 2dB. The precision of the resultant GPS position is +/- 0.010 m, with an absolute positional accuracy of 0.020 m + 5 ppm relative to the GPS base station, and with a GPS constellation having a PDOP of less than four (4). The antenna is mounted on the tail fin of the helicopter to prevent any signal interference by the rotor system and to prevent multi-pathing of the GPS signal.

SYSTEM ACCURACY 
The eagleeye system achieves excellent accuracy because of its highly accurate LiDAR unit and the integrated IMU and GPS systems. Accuracy varies based upon vegetation and terrain with expected levels of accuracy as follows :

Absolute Vertical Accuracy
+/- 0.5”- 2″ on hard surfaces
+/- 1”- 4” on soft or vegetated surfaces (flat/rolling)
+/- 1”- 6″ on soft/vegetated surfaces (hilly)

Absolute Horizontal Accuracy
+/- 1”-6” on all but extremely hilly terrain

Accuracy levels specified apply to post processed data and are at the 90% confidence level (RMSE).

FLIGHT PLANNING AND NAVIGATION 
Following client consultation to confirm project objectives and specifications, each job is thoroughly planned to achieve the desired accuracy, point spacing, and mapping contour. The flight altitude, helicopter speed, and flight lines spacing are customized for each project to meet specifications.

TrackAir digital navigation system is used to plan LiDAR swaths and digital camera centers and then exported to the helicopter computer system for flight guidance. The navigational system ensures accuracy by controlling both the LiDAR data recording and the digital camera. The nadir of the LiDAR sensor controls the critically important AGL height.

DATA PROCESSING 
Preliminary data processing is done on-site immediately after the data acquisition flight to verify coverage of the desired area. Subsequent processing is done by Tuck technicians to classify LiDAR points for identification of the ground and other features such as trees,buildings, transmission lines, etc. If specified, color photography, Digital Elevation Model (DEM) and/or digital orthophotography are prepared by trained Tuck technicians.

QUALITY CONTROL 
Quality is emphasized throughout all work processes beginning with a thorough client consultation to establish a clear understanding of the project and the desired deliverables. Detailed flight plans are prepared to acquire the desired mapping data and photography in accordance with the client specifications.

Accuracy is established at the beginning of the data acquisition flights through GPS benchmarks established on/near the project area upon initialization of the mapping system. GPS stations are established throughout the project area so that the helicopter is always within ten (10) miles of the station. Several surveyed ground control points in the mapped area are compared with the LiDAR data to determine any difference between the ground points and the aerial survey data. If any difference is identified, corrective adjustments are made and reported in the final project report.

The final project deliverables are reviewed and approved by a registered surveyor and/or certified photogrammetrist before delivery to the client.

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