Nelson and Tasman - Top of the South Flood LiDAR 1m DEM (2022)

Data Acquisition:

Airborne Laser Scanner (ALS) data was acquired from a fixed wing aircraft between 23 August 2022 and 6 September 2022, using Aerial Surveys Optech Galaxy PRIME laser scanner.

Survey Specification:

 Flying Height: 1,950 m AMGL
 Scan Angle: ±56 degrees
 Pulse Rate: 400 kHz
 Swath Overlap: 45%
 Swath Points Per M2: 2.8


Data Processing:

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

Base Station :PPRTX

The POS data was combined with the LiDAR range files and used to generate LIDAR point cloudsin 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.

LiDAR is relative to the control check points.

The positional accuracy of the LiDAR data has been checked by overlaying Sounds Surveying Ltdsurveyed 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 with TerraSolid LiDAR processing software into ground and above ground returns using automated routines tailored to the project landcover and terrain.

Please refer to survey reports for vertical/horizontal accuracy information.

Classification of the point cloud follows the classification scheme below:
1 - Unclassified
2 - Ground
3 - Low Vegetation
4 - Medium Vegetation
5 - High Vegetation
6 - Buildings
7 - Low Noise
8 - Model Key/Reserved
9 - Water
18 - High Noise

All spatial data for this project provided in terms of New Zealand Transverse Mercator 2000 (NZTM2000) horizontal and New Zealand Vertical Datum (NZVD2016). The data was converted from NZGD2000 ellipsoidal heights into the orthometric height system using the LINZ NZGeoid16 separation model. The products are tiled into NZTopo50 map sheet tiles as noted below.

The deliverables to LINZ were:

1m gridded bare earth digital elevation model (DEM)
1m gridded digital surface model (DSM)
Classified point cloud

All product deliverables supplied in terms of NZTM map projection and NZVD2016 vertical datum.