Data Acquisition:

Airborne Laser Scanner (ALS) data was acquired from a fixed wing aircraft between 12 and 30 May 2013, using Aerial Surveys' Optech ALTM 3100EA LiDAR system.

Survey Specification:

 Scanner: Optech ALTM 3100EA

 Flying height: 1250m AMGL

 Scan Angle: +/- 14.9 degrees

 Scan Frequency: 47.3Hz

 Pulse Rate 70kHz

 Swath Overlap: 35%

 Points Per Sqm: 1.24

Data processing:

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

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 C & R Surveyors . This was done by calculating

height differences statistics between the checkpoints and a TIN of the LiDAR ground points.

The standard deviation statistic is 0.03 m , a RMS of 0.03m and Average of 0.01m for Middle Waiau.

The standard deviation statistic is 0.03 m , a RMS of 0.07m and Average of -0.07m for Upper Hurunui, Pahau & Waitohi Areas.

The standard deviation statistic is 0.03 m , a RMS of 0.04m and Average of 0.01m for Hanmer Basin.

The standard deviation statistic is 0.03 m , a RMS of 0.06m and Average of -0.053m for Lower Hurunui, & the standard deviation statistc is 0.03, a RMS of 0.05m and Average of -0.03 for Lower Waiau.

The positional accuracy of the LiDAR data has been checked by overlaying C & R Surveyors

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 classified with TerraSolid LiDAR processing software into ground and above ground returns using automated routines tailored to the project landcover and terrain.

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

Classification of the point cloud followed the modified ASPRS classification scheme below:

0 - Created, never classified

2 - Ground

9 - Water

14 - Above_Ground

15 - River Stream points

17 - Water Body points

Re-processing:

In 2016 the data was reprocessed by Aerial Surveys for LINZrelative 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 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

Data hosted by OpenTopography was re-classified: the Above_Ground (14) points were reclassified as Unassigned classification (1)