ANZLIC Metadata Profile: An Australian/New Zealand Profile of AS/NZS ISO 19115:2005, Geographic information - Metadata
Metadata Standard Version
1.1
Reference System Info
Reference System
Reference System Identifier
Identifier
Code
2193
Identification Info
Data Identification
Citation
Citation
Title
Auckland South LiDAR 1m DEM (2016-2017)
Date
Abstract
This layer contains the DEM for LiDAR data in the southern Auckland Region captured between 2016 and 2017.
- The DSM is available as layer [Auckland South LiDAR 1m DSM (2016-2017)](https://data.linz.govt.nz/layer/104382).
- The index tiles are available as layer [Auckland South LiDAR Index Tiles (2016-2017)](https://data.linz.govt.nz/layer/104409).
- The LAS point cloud and vendor project reports are available from [OpenTopography](http://opentopo.sdsc.edu/datasets).
LiDAR was captured for Auckland Council by AAM New Zealand between September 2016 to June 2017. These datasets were generated by AAM New Zealand and their subcontractors. Data management and distribution is by 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 is 4 pulses/square metre.
Vertical Accuracy Specification is +/- 0.2m (95%).
Horizontal Accuracy Specification is +/- 0.6m (95%).
Released by LINZ under Creative Commons Attribution 4.0 New Zealand (CC BY 4.0) with:
Following Attribution: "Sourced from the LINZ Data Service and licensed by Auckland Council, for re-use under CC BY 4.0." For details see: https://www.linz.govt.nz/data/licensing-and-using-data/attributing-elevation-or-aerial-imagery-data
Data Acquisition: Airborne Laser Scanner (ALS) data was acquired from a fixed wing aircraft between 9 September 2016 and 6 February 2017, using AAM Riegl Q1560 LiDAR system.
The scan angle is < ±42 degrees per the data supplied to us not ±20 & 29 degrees referenced in the survey report specification. 18 LAS files are in LAS 1.2 format, the rest of the data is in LAS 1.3 format.
Airborne Laser Scanner (ALS) data was acquired from a fixed wing aircraft between 1 November 2016 to 29th June 2017 using AAM New Zealand's Riegl Q1560 - 2 laser channel system LiDAR system. This area includes Auckland Region covering southern suburbs and regions.
Classification of the point cloud followed the classification scheme below; 1 - Unclassified 2 - Ground 3 - Low Vegetation 4 - Medium Vegetation 5 - High Vegetation 6 - Buildings, Structures 7 - Low/High Points 9 - Water 10 - Bridge 12 - Overlap
Extra classifications found in three tiles were reclassified as Unclassified (1).
Rail (10) points were reclassified by LINZ as Bridges (17) per survey reference before providing the classified point cloud data to Open Topography.
Data Processing:
Reduction of the LiDAR data proceeded without any significant problems. Classification of the point clouds is to Level 3, with reference to ICSM LiDAR Specifications for NZ. Classification accuracy Required: 99% for ground points.
Discussion and clarification on Classification was undertaken between Nathan Sykes as client representative, and the AAM Team during the client review of the data, such as:
The pedestrian footbridges have been classed as structures, the intention was to use the bridge class for more substantial road bridges over water (unless it is a piped culvert)
Train carriages (temporary/moving objects) have been left in class 5, as assigned by classification routines.
The observation was made that the newer sensors, such as the Q1560, are very sensitive. They detect noticeably more atmospheric noise than older sensors (e.g. very light humidity that is not visible, can be detected). It’s not a defect. With these returns included and classified in the dataset, the user gets a feel for the structure of the data, e.g. in open areas where there are no “only returns” because the “first of many returns” are in the noise class.
The Digital Elevation (DEM) and Digital Surface Model (DSM) were derived using a point to TIN and TIN to Raster process, using Linear interpolation. Hydro flattening was undertaken in the DEM over non-tidal water bodies with surface area greater than 625 sq m, to the client specifications.
Tidal areas were flow within 1.5 hours of gazetted low tide (noting local variation in actual lowest water level)
Data Validation:
Ground data in this volume has been compared to test points obtained by field survey and assumed to be error-free.
Data classification has been manually checked and edited against any available imagery
Points to Note:
It was noted in tiles BB31_4425 and BB31_4325, there was significant flight line stepping between flights 2 and 10. This was caused by shifting sand dunes, rather than a system error.
The deliverables to LINZ were:
1m gridded bare earth digital elevation model (DEM) 1m gridded digital surface model (DSM) Classified point cloud
Metadata Constraints
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Copyright of this work is owned by Land Information New Zealand
