ALS (LiDAR) Survey - NSW Central and Hunter Coasts  

Authors / CoAuthors

Abstract

This suite of products relates to LiDAR data for the NSW Central and Hunter Coasts. The data was collected by Fugro Spatial Solutions Pty. Ltd. Under contract to the NSW State Government in January 2007. The survey was funded by the NSW Greenhouse Office (The Cabinet Office) with contributions from the Hunter Water Corporation and Lake Macquarie Council. LiDAR (Light Detection and Ranging) is an airborne remote sensing technique for rapid collection of terrain data. The sensor used for this LiDAR project collected XYZ and intensity data for two returns, first and last (ground) return by bouncing a pulse from the aircraft to the surface that enables the height and intensity values to be calculated. Survey report contains detailed information on capture and processing of LiDAR data Contract deliverable showing classified non-ground LiDAR strike returns recorded along survey flight lines. Point data records the surface elevation in metres AHD and intensity value of return. Data delivered as 1 square kilometre tiles for the entire survey area, a total of 1429 tiles covers the survey area. Survey report contains detailed information on capture and processing of LiDAR data. All data geo-referenced to GDA94/MGA56 and AHD. Survey report: Fugro Spatial Solution P/L, 2007, ALS Survey Report for Department of Planning (NSW) Central Coast, Fugro Spatial Solutions report J231335-20070309, March 2007.

Product Type

dataset

eCat Id

67218

Contact for the resource

Keywords

• DEM topographic

( Theme )

• marine

• AU-NSW

Australian and New Zealand Standard Research Classification (ANZSRC)

• Topology

• Published_Internal

Publication Date

2007-01-01T00:00:00

Creation Date

Security Constraints

Australian Government Security ClassificationSystem    

Classification - unclassified

Legal Constraints

Special, MOU, etc.

Access - restricted

Use - license

Status

Purpose

Maintenance Information

unknown

Topic Category

elevation

Series Information

Lineage

The NSW Department of Planning Central and Hunter Coasts LiDAR Project covers an area of some 1234 square kilometres between Wyong and Port Stephens on the NSW coast. Data intersects 1:100,000 map sheets NEWCASTLE 9232, LAKE MACQUARIE 9231 and GOSFORD 9131. Local government areas include NSW-PORT STEPHENS (A), NSW-NEWCASTLE (C), NSW-LAKE MACQUARIE (C) and NSW-WYONG (A). The full history of the source data and the processing steps are documented in the survey report. Fugro Spatial Solution P/L, 2007, ALS Survey Report for Department of Planning (NSW) Central Coast, Fugro Spatial Solutions report J231335-20070309, March 2007. Fugro Spatial Solutions acquired the LiDAR project using a Leica Geosystems ALS50-1+ Lidar system. The system was installed in a Cessna Titan 404 Aircraft. For the terrestrial elements of the project, four Novatel DL4 geodetic GPS receivers were employed. ALS Point Cloud Generation The Leica Geosystems ALS50-1+ sensor trajectory and LiDAR range measurements where integrated to produce the LiDAR point cloud. During this processing exercise the point clouds is generated and transformed to the MGA Zone 56 map grid, with elevations being reduced to AHD using the AUSGEOID98 geoid model. Each LiDAR measurement is output with GPS time & reflection intensity, with data being output in a per flight line fashion. ALS Point Cloud Processing The approach taken in processing LiDAR point clouds is primarily designed to derive a ground model that is accurate and clean. In order to achieve this any point that is not considered part of the clean surface (ie points from extreme edge of scan path or overlapping flight lines) is removed from the ground model and automatically classified as non-ground. This can result in certain flight line artefacts in non-ground data. Additional classification algorithms are required to process non-ground points in order to identify areas as vegetation, building etc. Data Import and Tiling Following removal of redundant flight lines, all flight lines where imported into a tiled Terrascan project format. Once the import process was completed a decimated version of the tiled dataset was loaded and inspected to ensure completeness of data coverage. Pre-process Filtering Once point cloud data was imported into a tiled format, each tile was filtered to isolate the ground surface returns from non ground surface returns. Measures where taken to ensure that low lying areas subject to tidal inundation where also isolated from the ground surface model. Flight Line Matching Areas where flight lines overlap where isolated and the ground surface models from individual flight lines compared to one another. A least squares surface matching application was employed to solve small systematic differences in sensor position (namely height) and orientation (namely roll). The differences solved for where in the order of the expected precision of the sensor trajectory, namely +/- 0.075m for height and +/- 0.005 degrees for roll. Elevations of ground check points where compared with those derived by construction a ground surface model from the LiDAR ground surface model. Expected accuracy for the Central Coast & Port Stephens ALS survey elevation data is quoted as +/-0.01m at 67% confidence (1 standard deviation) and +/-0.2m at 95% confidence (1.96 standard deviations) respectively for clear flat and open terrain. This exceeds the contract specification for 0.15m at 67% confidence (1 standard deviation). Contour Generation. From the ground classified ALS point cloud a decimated, non gridded set of points, at a resolution of about 1 point every 2.5 meters is created. From these points, triangles are being built. At 0.5m intervals in height points or interpolated points on triangle edges with that same height are being connected using smoothed curved lines. The lines for each height interval are then connected to become the final contours.

Parent Information

Extents

[-33.407, -32.7098, 151.3018, 151.8934]

Reference System

Spatial Resolution

Service Information

Associations

Downloads and Links

Source Information

In January 2006, Fugro Spatial Solutions Pty Ltd was contracted by Department of Planning NSW to acquire ALS data over an area of approximately 1260 square kilometers in the vicinity of Newcastle, New South Wales. Please note the figures in this report also include an adjoining area covering the Port Stephens LGA, with an additional area of approximately 360 square kilometers. The main aims of this report are to; - Describe the survey equipment used on this project - Describe the survey method used for geodetic elements of the project - Describe the survey method used for airborne elements of the project - Explain the method used to pre-process the ALS point cloud and verify the accuracies obtained - Summarise the overall findings The required vertical and horizontal accuracies as per the contract were Vertical ±150 mm RMSE (67% CI) Horizontal ±600 mm RMSE (67% CI) The Central Coast ALS survey was completed in four survey flights, occurring on the 10th, 11th & 12th of January 2007. The geodetic elements of the survey where commenced with base station deployment on the 8th of January 2007. Geodetic observations occurred on 9th, 10th, 11th, 12th & 13th of January 2007. Airborne operations where conducted from Williamstown Airport for the duration of the survey. The Port Stephens ALS survey was completed in two survey flights, occurring on the 15th & 16th of January 2007. The geodetic elements of the survey where commenced with base station deployment on the 13th of January 2007. Geodetic observations occurred on 14th & 15th of January 2007. Airborne operations where also conducted from Williamstown Airport for the duration of the survey.