Data Acquisition:

Airborne Laser Scanner (ALS) data was acquired from a fixed wing aircraft on:

7th, 8th, 18th ,19th February & 1st March 2015, using Aerial Surveys OptechOrion H300 LiDAR system.

Survey Specification:

• Scanner: Optech Orion H300

• Flying Height: 500m AMGL

• Scan Angle: ±10.4 degrees

• Scan Frequency: 60.3Hz

• Pulse Rate: 50kHz

• Swath Overlap: 35%

• Points Per M2: 4.02

Data processing:

The LiDAR sensor positioning and orientation (POS) was determined using the collected

GPS/IMU datasets and Applanix POSPac software.

Benchmark: GSAM (Amberly) OWNER: Global Surveys

Base Station:

Type/Owner: VRS Geosystems

Benchmark: BS02 Based on our control point MOR101

Base Station Position:

39 10 44.39864 S 176 37 48.07897 E 406.311 Ell Height

Antenna Height:

2.250 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 0.041m; a RMS of 0.069m and the average difference is -0.055m.

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 are supplied in terms of NZTM map projection.

Classification of the point cloud followed the classification scheme below:

0 - Created, never classified

2 - Ground

14 - Above_Ground

Re-processing:

In 2016 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 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)