Marlborough LiDAR 1m DSM (2018)

Survey Specification:

-Device Name: Optech Orion H300
-Half Scan Angle: 30 degrees
-Laser Pulse Rate: 250 kHz
-Laser Pulse Mode: Multi Pulse
-Laser return: 1st, 2nd, 3rd and last
-Laser Intensity: All Returns
-File Format: ESRI ASCII Grid, LAS 1.2, ESRI Shapefile
-Horizontal Datum: NZGD2000
-Vertical Datum: NZVD2016
-Map Projection: NZTM2000
-Vertical Accuracy Specification: ±0.2m Standard Error (68% confidence level or 1 sigma)
-Horizontal Accuracy Specification: ±1.0m Standard Error (68% confidence level or 1 sigma)


Airbourne Laser Scanner (ALS) data was acquired from a fixed wing aircraft between 26th May to 12th September 2018 using AAM New Zealand's Optech Orion H300 LiDAR system. This area includes the Flaxbourne River, Lake Grassmere, Seddon, Lower Awatere Valley, Picton, Waikawa, the Wairau Valley and Plains, including Spring Creek, Tuamarina and parts of Blenheim in 2018.

Classification of the point cloud followed the classification scheme below;

1 - Default
2 - Ground
9 - Water

Data Validation:
Ground data in this volume has been compared to 724 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 field survey of check sites completed by Sound Surveying Ltd allowed an assessment of the accuracy of the ALS data.

Sounds Surveying observed several of the LINZ geodetic marks near the check site locations. Irregular shifts were observed at some sites, and we note that LINZ downgraded the order on many of the points in this area on 1 August 2018.

As a result, the field survey of Test Points in the Cape Campbell area was computed relative to Cape Campbell No 2 CORS site (CMBL, coordinates as authorized on 14 Jan 2018), no adjustment was made relative to the local geodetic marks.

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 2.

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.

Breaklines have been used where required to ensure hydro flattening on the DEM products. Lakes and large rivers were hydroflattened in the Bare Earth Digital Elevation Model.