Canterbury - Mackenzie LiDAR 1m DEM (2015)

Data Acquisition:
Airborne Laser Scanner (ALS) data was acquired from a fixed wing aircraft on:
10 &11 February 2015, using Aerial Surveys OptechOrion H300 LiDAR system.

Survey Specification:
• Scanner: Optech Orion H300
• Flying Height: 1500m AMGL
• Scan Angle: ±20 degrees
• Scan Frequency: 30.7Hz
• Pulse Rate: 75kHz
• Swath Overlap: 35%
• Points Per M2: 1

Data processing:

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

Benchmark: PUKAKI

Base Station Positions:

44 14 07.433570 S 170 07 00.766050 E 483.949 Ell Height

Antenna Height:

For 10th 1.401M for 11th 1.485M phase center

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 0.038m; a RMS of 0.045m and the average difference is 0.022m. 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 withTerraSolid LiDAR processing software into ground and above ground returns using automated routines tailored to the project landcover and terrain.

All product deliverables supplied in terms of NZTM map projection and NZVD2016 height datum.

Classification of the point cloud followed the classification scheme below:
2 - Ground
14 - Above Ground

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 Classified Point Cloud Data was reclassified by LINZ and is hosted by Open Topography: the Above_Ground (14) points were reclassified as Unassigned classification (1).