Topic category

• Elevation

Use limitation

General 

Classification

Unclassified  

Description

Digital Elevation Model (DEM) - The DEM was generated from the point cloud (class 2 - Ground). Terrain Grids were derived using LasTools las2dem. This software reads LIDAR points from the LAS/LAZformat, triangulates them temporarily into a TIN, and then rasterises the TIN onto a DEM. Standard linear interpolation is used. Bridge Removal – bridges have been classified and excluded from DEM generation. Additional synthetic points were collected to support the DEM shape when bridges and culverts were removed. These points have only been introduced into the DEM processing, to avoid triangulation across the bridge or culvert. Hydro-flattening was undertaken as per DELWP guidelines. Hydro-flattening features are drawn manually to define the following: Non-tidal water bodies with surface area greater than 625m2 Non-tidal water courses greater than 30m nominal width are hydroflattened as appropriate for the gradient of the river. Braided rivers with shingle beds are treated as ground. Tidal variation – AAM recommend clipping/masking coastal water from the DEM, while retaining all valid offshore rocks and islands. This gives a clean presentation around the coastline and includes all valid ground data. Areas outside the coastal boundary have "no data” value applied to the full tile extents. Hydro Features are drawn with reference to the point cloud and intensity images to define water boundaries and ocean clipping boundaries for tidal water areas. These are used to generate points to fill the water bodies with height extracted from the lowest surrounding ground points. For sloping rivers, a manual approach is required to define cross-sections of river where the gradient changes to apply sloping heights accordingly. Ground classified points, hydro-flattening points and synthetic points for bridge and culvert removal are combined to form the input data for DEM generation using Point to TIN, and TIN to Raster Natural Neighbour interpolation. 

Classification

Unclassified  

Attribute Quality

Positional Accuracy

Conceptual Consistency

Comments

All raster values are within expected data ranges. 

Missing Data

Comments

The raster data set consists of full data tiles (no null space) and the extent and coverage is common with the other datasets in this project. 

Excess Data

Platform Type

Aerial  

Assembly

Single  

Tile Size

1 km  

Raster Type

DEM  

X Pixel Resolution (cm)

1cm  

Y Pixel Resolution (cm)

1cm  

Seamlessness

Full  

Number of Bands

1 

Band List

1  

Resampling Kernel

Not Entered  

Rectification Type

Not Entered  

Platform Name

Fixed Wing Aircraft  

DEM Creator

Supplier