Survey Specification:

-Device Name: ALS 60

-Half Scan Angle: 30 degrees

-Laser Pulse Rate: 300 kHz

-Laser Pulse Mode: Multi Pulse

-Average Point Spacing: 2.0 pts/m2

-Laser return: 1st, 2nd, 3rd and last

-File Format: ESRI ASCII Grid, LAS 1.3, ESRI Shapefile

-Horizontal Datum: NZGD2000

-Vertical Datum: NZVD2016

-Map Projection: NZTM2000

-Vertical Accuracy Specification: ±0.06m Standard Error (68% confidence level or 1 sigma)

-Horizontal Accuracy Specification: ±0.50m Standard Error (68% confidence level or 1 sigma)

Note: Point Cloud Data from vendor has been supplied in LAS 1.3 format, despite Survey Report stating that it was supplied in LAS1.2 format.

Airborne Laser Scanner (ALS) data was acquired from a fixed wing aircraft between 13th and 14th December 2016 using AAM New Zealand's Leica ALS60 LiDAR systems. This area included coastal areas from Riwaka in the South to Onekaka in the North.

Classification of the point cloud followed the classification scheme below;

1 - Default

2 - Ground

3 - Low Vegetation

4 - Medium Vegetation

5 - High Vegetation

9 - Water

Data Validation:

Ground data in this volume has been compared to 468 test points obtained by field survey and assumed to be error-free. The test points were distributed across the mapping area and located on clear open ground. The mean difference has been removed from the data.

Data Classification has been manually checked and edited against any available imagery.

Limitations of Data:

The definition of the ground under trees may be less accurate.

Ground Support

GPS base station support was sourced from GeoNET CORS. The ground check points surveyed by Sound Surveying Ltd allowed an assessment of the accuracy of the ALS data.

Data Processing:

Reduction of the ALS data proceeded without any significant problems. Laser strikes were classified into ground and non-ground points using a single algorithm across the project area. Manual checking and editing of the data classification further improved the quality of the terrain model. Ground and water classes have been classified to ICSM Level 3.

ArcGIS 10.1 Terrain Grids were derived using the Natural Neighbour interpolation. This method uses the closest triangles and applies weights to the proportionate areas from the grid cell centroid to interpolate the value. It uses known elevation data, it does not make any predictions regarding the surface and accurately depicts existing troughs and peaks in the data and supports irregular point spacing, which suits the nature LiDAR data.

Lakes and large rivers were hydroflattened in the Bare Earth Digital Elevation Model.