Merged Tiles - Ausgeoid09 - DEM

dataset
Dataset: Merged Tiles - Ausgeoid09 - DEM Assembly: Single
 
Citation proposal Citation proposal

Merged Tiles - Ausgeoid09 - DEM

Department of Transport and Planning

Description

Title
Merged Tiles - Ausgeoid09 - DEM 
 
 

Temporal

Time period
2012-02-062012-03-09 
 
 

Spatial

Horizontal Accuracy
0.3m 
Vertical Accuracy
0.1m 
Code
MGA Zone 55 GDA94 
 
 

Format

Title
ESRI Ascii 
 
 

Contacts

  Point of contact

  Custodian

 
 

Keywords

Topic category
  • Elevation
 
 

Resource Constraints

Use limitation
General 
Classification
Unclassified 
 
 

Lineage

Description
The surrounding adjacent LiDAR projects incorporated in the merged tiles are: 2011 Melbourne Structural Vegatation LiDAR - Lara, Victorian Coastal LIDAR Level 3 Classification, 2013-14 Geelong-Anakie-Golden Plains LiDAR 1) ArcGIS 10 Terrain Grids were derived using the Natural Neighbor interpolation. This method uses the closest triangles and applies weights to the proportionate areas from the grid cell centroid to interpolate the value. It uses known elevation data, it does not make any predictions regarding the surface and accurately depicts existing troughs and peaks in the data and supports irregular point spacing, which suits the nature LiDAR data. Grids were then translated to ESRI ASCII formats using custom ArcGIS and Feature Manipulation Engine (FME) macros. 2) For comparison, two separate datasets were generated, one referenced to AHD using Ausgeoid09 and a 2nd dataset referenced to AHD using Melbourne Geoid model. The dataset referenced to AHD using Ausgeoid09 reveals a marginally better fit to test points. A tilt in a general east-west direction was observed when the LiDAR data was compared to field test point sites spread throughout the project area. A tilt correction has been applied to both Ausgeoid09 and Melbourne Geoid datasets. 4) Cut lines were used to merge the adjacent datasets together. An overlap of 50m was used between adjacent/overlapping datasets. Cut lines have been made around ground features that have changed between the dates of the new and existing data within overlap areas. New reprocessed data has been kept in preference to existing data. Below are approximate locations of where changes in ground features have occurred. Adjustments to cut lines have been made in these locations: 264590E, 5773165N; 269210E, 5771650N; 270540E, 5757320N; 271690E, 5770390N 
 
 

Metadata Constraints Metadata Constraints

Classification
Unclassified 
 
 

Quality

Attribute Quality
Positional Accuracy
Conceptual Consistency
Comments
Meets all specifications and adheres to format and naming standards. An assessment of the merged tiles for DTM consistency was undertaken across all project edges. In general the edgematching was adequate and any stepping between source datasets is within reasonable limits. However, in one particular instance, the redevelopment and widening of the Midland Highway between the dates of the 2 LiDAR surveys in question has resulted in a significant step (>0.25cm and up to 0.6m) in the merged product. This is an unfortunate and unavoidable effect of mergeing data over changed land surfaces. 
 
Missing Data
Comments
This data set represents the edge tiles of the original AOI that have overlap with adjacent projects.The tiles are full with respect to data content and consist of merged data from the source project and the adjacent projects. 
 
Excess Data
 
 

Acquisition Info

Platform Type
Aerial 
Assembly
Single 
Tile Size
2 km 
 
 

Raster Data Details

Raster Type
DEM 
X Pixel Resolution (cm)
1cm 
Y Pixel Resolution (cm)
1cm 
Seamlessness
Full 
Number of Bands
1 
Band List
1 
Resampling Kernel
Cubic Convolution 
Rectification Type
Orthorectified 
Platform Name
Fixed Wing Aircraft 
 
 

Raster Type Details

DEM Creator
Supplier 
 
 

Survey Details

Sensor

Title
Optech ALTM Orion 
Identifier
Aerial

Type
LIDAR 
Cloud Cover Percentage
0 
 

Aerial Survey Details

Runs
83 
Run Orientation
Various 
Swath Width
807 
Side Overlap
25 
Forward Overlap
100 
Flying Height Unit
agl metre 
Flight Height
1200 
 
 


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