Otago - Queenstown LiDAR Index Tiles (2021)

Otago - Queenstown LiDAR Index Tiles (2021)

Toitū Te Whenua Land Information New Zealand

2021-03-13

This layer contains the Index Tiles for LiDAR data in the Otago Region, north of Lake Wakatipu and surrounding Queenstown and Arrowtown, captured in 2021.

- The DEM is available as layer [Otago - Queenstown LiDAR 1m DEM (2021)](https://data.linz.govt.nz/layer/105898).

- The DSM is available as layer [Otago - Queenstown LiDAR 1m DSM (2021)](https://data.linz.govt.nz/layer/105855).

- The LAS point cloud and vendor project reports are available from [OpenTopography](https://portal.opentopography.org/datasets?loc=New%20Zealand).

LiDAR was captured for the Queenstown Lakes District Council by Landpro on the 13th and 14th of March 2021. These datasets were generated by Landpro Ltd and their subcontractors. Data management and distribution is by Toitū Te Whenua Land Information New Zealand.

Data comprises:

- DEM: tif or asc tiles in NZTM2000 projection, tiled into a 1:1,000 tile layout

- DSM: tif or asc tiles in NZTM2000 projection, tiled into a 1:1,000 tile layout

- Point cloud: las tiles in NZTM2000 projection, tiled into a 1:1,000 tile layout

Pulse density specification is at a minimum of >4 pulses/square metre.

Vertical accuracy specification is +/- 0.2 m (95%).

Horizontal accuracy specification is +/- 1.0 m (95%).

Vertical datum is NZVD2016.

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

-45.11449359938098 168.61071874412224 -44.92726866375254 168.86977395662012

https://data.linz.govt.nz/layer/105905-otago-queenstown-lidar-index-tiles-2021/

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