Topic category

• Elevation

 

Use limitation

General 

Classification

Unclassified  

 

Description

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 manifests 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 - Riegl) being applied to all flights of LiDAR data in this project. This delayed production for approximately three weeks. Reduction of the LiDAR data proceeded without any significant problems, Laser strikes were classified into ground and non-ground points using a single algorithm across the project area. Manual checking and editing of the data classification further improved the quality of the terrain model. 

 

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. This data has been classified to an ICSM level 2 standard where there is an emphasis on ground classification accuracy only. 

Missing Data

Comments

The point cloud data is complete for the defined project extent. Gaps may occur due to diminished returns over water, under canopy and on materials with low laser reflectivity, such as black roofing or swimming pools. 

Excess Data

 

Platform Type

Aerial  

Assembly

Single  

Tile Size

2 km  

 

 

Pulse Mode

Multi Pulse 

Scan Rate (Hz)

102Hz  

Scan Frequency (kHz)

330kHz  

Scan Angle (degrees)

60degrees  

Footprint Size (m)

0.33500001m  

Point Density Actual (pts/m2)

0.06points/m2  

Point Spacing Actual (pts/m)

4points/m2  

Ellipsoid Provided

1 

Ellipsoid Vertical Datum

AUSGEOID09  

Ellipsoid Format

LAS 1.3  

Geoid Vertical Datum

AUSGEOID09  

Additional Adjustments

Ground data in this volume has been compared to 270 test points obtained by field survey and assumed to be error-free. The test points were distributed in three groups across the mapping area and located on open clear ground. Comparison of the field test points with elevations interpolated from measured data for the three sites resulted in 0.943, 0.891 & 0.885 RMS (m). The mean difference at each site has been removed from the data. Final accuracy estimates after removing the mean offsets yielded 0.031, 0.032 & 0.016 RMS(m). 

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	1