Data Acquisition:

Airborne Laser Scanner (ALS) data was acquired from a fixed wing aircraft on between 27 December 2015 and 17 December 2016, using Aerial Surveys OptechOrion H300 LiDAR system.

Survey Specification:

• Scanner: Optech Orion H300

• Points Per M2: 2 or greater

For details about flying height, scan angle, scan frequency, pulse rate and swath overlap please refer to the survey report.

Data Processing:

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

For Benchmark and Base Station information, please refer to the survey report.

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 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.

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:

This 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).