Title

Mallee CMA - DTM 

Resource Type

Dataset  

Spatial representation type

Grid  

Horizontal Accuracy

0.3m  

Code

MGA Zone 54 GDA2020 

 

Title

ESRI Ascii 

Topic category

• Elevation

Use limitation

General 

Classification

Unclassified  

Description

The DTM was primarily generated from the point cloud class 2 (ground). Class 9 (water) was also used in the DTM in order to form a continuous surface across the river channel where DTM interpolation could not fill data voids caused by water. The decision to include water points in the DTM was based on the following: - Hydro flattening of the river channel was not undertaken. The hydro flattening would normally infill the river channel area with (flat) surface data, regardless of lidar returns from the water surface. However, without the hydro flattening process, large void spaces would be present in the river channel area if only ground points were used. - Hydro flattening was not undertaken because the process relies on the manual delineation of where the water line finishes and channel bank begins in the point cloud classification stage. For the purposes of the project, it was important for this delineation to be undertaken using the Frontier-SI River Line Toolkit. - Although void areas could have solely been filled in by a TIN interpolation process, the preference was to utilise all available LiDAR returns from the channel area (ie; points classified as water) and then rely on TIN interpolation where no LiDAR points were available. ArcGIS 9.2 Terrain Grids were derived using las2dem. This tool reads LIDAR points from the LAS/LAZ format (or some ASCII formats), triangulates them temporarily into a TIN, and then rasters the TIN onto a DTM. 

Classification

Unclassified