Title

Little Desert - LiDAR 

 

Time period

2016-01-092016-01-10 

 

Horizontal Accuracy

0.3m  

Vertical Accuracy

0.1m  

Code

MGA Zone 54 GDA94 

 

 

Title

LAS 1.3, Waveform Packets 

 

 

Topic category

• Elevation

 

Use limitation

General 

Classification

Unclassified  

 

Description

LiDAR was acquired over the project area. An instrument calibration issue was encountered with the LiDAR system during initial pre-processing. The issue was caused by an internal calibration error between channel 1 and channel 2. It manifested itself by producing a fluctuating, vertical, misalignment between both channels in the range of 0.05 - 0.20m (relative accuracy). It was resolved by an internal calibration correction (provided by sensor manufacturer) being applied to all flights of LiDAR data in this project. The acquired LiDAR strikes were transformed into an ellipsoid point cloud using a solution obtained from the onboard IMU and GPS and Victorian CORS network. The point cloud was then adjusted to AHD using AusGeoid09. Checks against an network of surveyed ground control resulted in further general and local adjustments where required. Reduction of the LiDAR data proceeded without any significant problems. Laser returns were classified into ground and non ground classes using a single algorithm tailored to the project before further automatic classification was performed to differentiate non ground features into their respective classes. Following this, manual checking and editing was undertaken to improve the classification of the ground class. 

 

Classification

Unclassified  

 

Attribute Quality

Positional Accuracy

Conceptual Consistency

Comments

Accuracy of the ground surface under dense canopy may be reduced due to diminished returns. Laser accuracy at swath edges may be reduced. Classification algorithms have been tailored for common terrain/vegetation combinations across the project area. Classification accuracy and ground definition may be less accurate in uncommon or mixed terrain/vegetation/land use combinations. The Riegl Q1560 LiDAR sensor is an extremely sensitive system and also contains a unique functionality with ¿multi-time-around¿ technology. The combination of these two factors increases the number of high/low outliers compared to other LiDAR sensors. 

Missing Data

Comments

Gaps may occur due to the multi-time-around technology of the Reigl Q1560 LiDAR Sensor, or from diminished returns over water, under canopy and on materials with low laser reflectivity, such as black roofing, swimming pools. 

Excess Data

 

Platform Type

Aerial  

Assembly

Single  

Tile Size

2 km  

 

 

Pulse Mode

Multi Pulse 

Scan Rate (Hz)

102Hz  

Scan Frequency (kHz)

400kHz  

Scan Angle (degrees)

60degrees  

Footprint Size (m)

0.25m  

Point Density Actual (pts/m2)

4points/m2  

Point Spacing Actual (pts/m)

0.5points/m2  

Ellipsoid Provided

1 

Ellipsoid Vertical Datum

GRS80 Ellipsoidal (ITRF2005)  

Ellipsoid Format

LAS 1.2  

Geoid Vertical Datum

AUSGEOID09  

Additional Adjustments

Ground data in this volume has been compared to 364 test points obtained by field survey and assumed to be error-free. The test points were distributed in 4 groups across the mapping area and located on open clear ground. Comparison of the field test points with elevations interpolated from measured data resulted in the mean difference for Horsham (-0.918m) being removed from the data. 

Class Level

2 

Classification Accuracy

98 

Classification

Class Level	Classification Accuracy	Class 0 - Unclassified	Class 1 - Default	Class 2 - Ground	Class 3 - Low Vegetation	Class 4 - Medium Vegetation	Class 5 - High Vegetation	Class 6 - Buildings/Structures	Class 7 - Low/High Points	Class 8 - Model Key Points	Class 9- Water	Class 10 - Bridge	Class 12 - Flightline Overlap Points
2	98	1	1	1	1	1	1	1	1	1	1	1	0