Data Acquisition:

Airborne Laser Scanner (ALS) data was acquired from a fixed wing aircraft on 13th and 14th of March 2021 using Landpro's Leica ALS60 LiDAR system.

Data Processing:

The LiDAR sensor positioning and orientation (POS) was determined using the collected GNSS/IMU datasets, which was processed utilising GSQU Base Station and precise ephemeris data.

The GNSS and IMU are processed in a tightly coupled loop to give an optimum trajectory. This 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 CloudPro processing software.

The point cloud data was then classified with TerraSolid's TerraScan LiDAR processing software into ground and above ground returns. A manual classification was done over the required area to edit the points with gross classification errors that may have occurred in the automatic classification process. Scanner edges were cut by 2 degrees to ensure maximum point density.

The check points have been compared with the LiDAR ground surface and used as a vertical check on the data. The standard deviation statistic is 0.03 m; a RMS of 0.03 m and the average magnitude is 0.02 m.

The positional accuracy of the LiDAR data has been checked by plotting the Landpro Ltd. check points and displaying the LiDAR by intensity. The LiDAR was found to be in position.

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

LINZ re-classification of the point cloud files followed the classification scheme below:

1 - Unclassified

2 - Ground

3 - Low Vegetation

4 - Medium Vegetation

5 - High Vegetation

6 - Building

7 - Low Point (noise)

9 - Water

18 - High Noise

LINZ also removed spikes from the Bare Earth Digital Elevation Model, found at tiles:

DEM_CB11_2021_1000_4822

DEM_CC11_2021_1000_0812

DEM_CC11_2021_1000_0912

DEM_CC11_2021_1000_0914

DEM_CC11_2021_1000_1007

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

Disclaimers with this dataset:

Intensity range has not been normalised for the whole point cloud dataset.

Incorrect format of GPS time for 331 point cloud files.

Inconsistent pixel sizes:

DEM_CB11_2021_1000_4233

DEM_CB11_2021_1000_4234

DEM_CC11_2021_1000_0413

DEM_CC11_2021_1000_0414

DSM_CB11_2021_1000_4233

DSM_CB11_2021_1000_4234

The deliverables to LINZ were:

1m gridded bare earth digital elevation model (DEM)

1m gridded digital surface model (DSM)

Classified point cloud