Otago - Queenstown LiDAR Index Tiles (2016)

Data Acquisition:
Airborne Laser Scanner (ALS) data was acquired from a fixed wing aircraft on:
2nd, 4th, 5th, 6th, 18th, 19th March and 21st April 2016 using Aerial Surveys OptechOrion H300 LiDAR system.

Survey Specifications:
• Scanner: Optech Orion H300
• Flying Height: 2100m AMGL
• Scan Angle: ±22 degrees
• Scan Frequency: 48Hz
• Pulse Rate: 125kHz
• Swath Overlap: 30%
• Points Per M2: 2.06

Data processing:

The LiDAR sensor positioning and orientation (POS) was determined using the collected
GPS/IMU datasets and Applanix POSPac software.

Benchmark 1: VZQN (Queenstown Glenda) OWNER: Geosystems

Base Station Position: -45 00 34.77762 S 168 45 11.54995 E 373.521 Ell Ht

Antenna Height: 0.085 Phase Center

Benchmark 2: GSQU OWNER: Global

Base Station Position: -44 58 31.16085 S 168 45 52.01762 E 384.4

Antenna Height: 0.000 Phase Centre

The POS data was combined with the LiDAR range files and used to generate LIDAR point clouds in NZTM and ellipsoidal heights. This process was undertaken using Optech LMS LiDAR processing software. The data was checked for completeness of coverage. The relative fit of data in the overlap between strips was also checked.

The height accuracy of the ground classified LiDAR points was checked using open land-cover survey check site data collected by Sounds Surveying Ltd. This was done by calculating height differences statistics between a TIN of the LiDAR ground points and the checkpoints. The standard deviation statistic is 0.022m; a RMS of 0.023m and the average difference is 0.006m. LiDAR is relative to the control check points.

The positional accuracy of the LiDAR data has been checked by overlaying Sounds Surveying Ltd surveyed data over the LiDAR data displayed coded by intensity. The data was found to fit well in position.

The point cloud data was then classified with TerraSolid LiDAR processing software into ground and above ground returns using automated routines tailored to the project landcover and terrain.

All product deliverables are supplied in terms of NZTM map projection.

For the classification scheme of the point cloud please refer to the original survey report.

Re-processing:
In 2018 the data was reprocessed by Aerial Surveys for LINZ relative to the NZVD2016 vertical datum, and supplied as 1:1000 nominal scale (2500 720m high x 480m wide subtiles per full NZ Topo50 sheet). Lakes and large rivers were hydroflattened in the Bare Earth Digital Elevation Model. The deliverables to LINZ were:

1m gridded bare earth digital elevation model (DEM)
1m gridded digital surface model (DSM)
Classified point cloud

Reprocessed Point Cloud Data was reclassified by LINZ, points classified as 3 - Above Ground were reclassifed to 1 - Unassigned.

Classification of the Point Cloud available on Open Topography are as follows;

1 - Unassigned
2 - Ground