Title

Vicmap Elevation - Coastal 1m DEM & 0.5m Contours 

Alternate title

VICMAP_ELEV_COASTAL_TOPO_DEM_CONTOUR 

Purpose

Vicmap Elevation provides an accurate representation of natural relief features along the coast of Victoria. It is used in a variety of applications,including planning and environmental modelling. 

Supplemental Information

Related Documents: None Please see Vicmap Elevation - Coastal 1m DEM & 0.5m Contours product description for more detailed information on this product. This can be found on the Vicmap Elevation Webpage. https://www.land.vic.gov.au/maps-and-spatial/spatial-data/vicmap-catalogue 

Status

Obsolete  

Code

28354 

Maintenance and update frequency

Not planned  

Title

Both the 1m DEM and 0.5m Contours are stored in 2x2km Tiles Native Format: DEM- XYZ ASCII. ESRI Grid ASCII Contours - ESRI Shapefile, MapInfo TAB 4 

Topic category

• Elevation
• Environment
• Geoscientific information

Use limitation

Victorian Government departments, agencies and Local Government Authorities can access the data by e-mailing the point of contact. 

Classification

Unclassified  

Statement

Dataset Source: The Vicmap Elevation - Coastal 1m DEM & 0.5m Contours was derived from airborne LIDAR specifically acquired for this dataset between September 2007 and September 2009. The irregular LiDAR points used to derive this product are not currently available. This data has been acquired through the Coordinated Imagery Program to support the Victorian Governments Future Coasts Project. Dataset Originality: Primary & Derived 

Description

Collection Method: Airborne LiDAR 

Description

Raw LiDAR Points were used to generate a "bare-earth" DEM and contour datasets. The raw LiDAR points were classified into ground and non-ground irregulary spaced points using a specifically designed algorithms applied across the entire project area. The quality of the classification was further improved by manual checking and editing of the LiDAR points using intensity imagery and orthophoto imagery as a reference. The definition of ground under trees or heavily vegetated areas may be less accurate. To generate the Coastal 1m DEM the ground points were imported to a "point" feature class in ESRI ArcGIS. Following the import to ESRI format, the points were converted to a Terrain Data Type and then interpolated into regularly spaced 1m grids. The generation of the Coastal 0.5m Contours are created by referencing the all ground LiDAR strikes. A number of macros are applied to the all ground strikes before contour generation. These macros thin and smooth the LiDAR ground strikes. Contours are then generated automatically from the smoothed LiDAR strikes. Contours are derived by interpolation of a surface model generated from LiDAR ground points using process parameters optimized to suit the terrain. The contours are then checked using any available imagery as a backdrop and line work cleaned where required. Final macros are applied to the contour lines that check for dangles, loops, spikes etc.. Both the 1m DEM and 0.5m Contours where quality checked against imagery and other elevation sources. This includes identifying gross errors in height values, removing stepping within the DEM and ensuring all contours are correctly edge matched. 

Classification

Unclassified  

Attribute Quality

Comments

The vertical accuracy associated with the DEMs is +/-10cm @ 68% confidence or better in areas of bare ground. Reprojecting, changing format or resampling causes changes to the height values in the DEM. The vertical accuracy associated with the contours is such that 95% of "well defined" points along the contour line have a value that must not differ to the "true" ground surface by any more then half of the contour interval, in this case 25cm. 

Positional Accuracy

Comments

The horizontal accuracy for both the DEM and contour datasets is +/-35cm 

Conceptual Consistency

Comments

The DEM values across initial basin tiles have been constructed to ensure smooth consistent elevation values is achieved. The contours are consistent for contour interval, smoothness, cartographic display and elevation attribution. Logical consistency is a measure of the degree to which data complies with the technical specification. The test procedures include a mixture of scripts and on-screen visual checks. 

Missing Data

Comments

This terrestrial dataset is only along the Victorian coast and inland to approximately the 10m elevation line. 

Excess Data