Title

Satellite Image Colour Mosaic (30 metre pixel) - Vicmap Imagery (Satellite) 

Alternate title

TM7-2000VI30 

Purpose

Vicmap Imagery TM7-2000VI30 will be useful as a backdrop for many data visualisation purposes including map production, spatial and thematic interrogation of vector datasets and in presentation and demonstration material. It will be useable at scales of 1:50,000 and smaller. Additionally, Vicmap Imagery TM7-2000VI30 can be used for visual interpretation of land cover features. Vicmap Imagery TM7-2000VI30 will not be applicable for digital classification purposes, as the digital values have been modified for visual appeal. For any such requirements, the raw component imagery should be used. 

Supplemental Information

Relationship to other Datasets: Vicmap Imagery TM7-2000 is be an updated version of the existing image catalogue images currently provided in the NRE Corporate Geospatial Data Library. Related Documents: VMDIProductDescript4c.doc. - VicMap Digital Image Product Description 

Status

Completed  

Horizontal Accuracy

30m  

Maintenance and update frequency

As needed  

Title

compressed ecw and 8 bit tiff 3 

Topic category

• Imagery base maps earth cover

Use limitation

VicMap Digital Image products are provided under the terms and conditions of an annual licence. 

Classification

Unclassified  

Statement

Dataset Source: Vicmap Imagery TM7-2000 is a derived product developed by the Land Information Group. The source Landsat 7 ETM+ imagery is purchased from ACRES. The product name for the imagery purchased from ACRES is Path Image, or Level 1G. The product name represents the level of radiometric and geometric processing performed by ACRES on the data. The Path Image, or Level 1G product, has been radiometrically corrected and resampled to suit geometric correction and registration to a geographic map projection. In all, sixteen images were required to provide statewide coverage of Victoria. Vicmap Imagery TM7-2000 is a static product. Once created it remains unchanged until the next annual update replaces it. The lineage for this product is therefore relatively short. Dataset Originality: Derived 

Description

The process of creating a seamless mosaic from images of different dates requires that the images be enhanced. Image enhancement helps ensure that like features have the same appearances across all images. However, the process may generalise the clarity of some features, as well as increase the sharpness of other features. The process of image enhancement aims to strike a balance between the optimum representation of the major land cover types across the State. 

Classification

Unclassified  

Attribute Quality

Comments

There are no attributes attached to the Vicmap Imagery TM7 2000. All associated information is provided through the standard NRE metadata protocol. Generally, the physical size of the features and the spatial resolution of the ETM+ sensors determine the clarity and sharpness with which those features can be identified. However, the colour contrast within and the colour balance between images can be manipulated to produce a mosaic that is both visually appealing and thematically rich in content. The level of success in achieving this outcome is subjective. 

Positional Accuracy

Comments

All component images used in Vicmap Imagery mosaics are georeferenced to the Vicmap Transport - Roads network using an average of twenty evenly spread control points per image. Additionally, component images over the eastern and southern Victorian highlands have been georeferenced using elevation models from the Vicmap Elevation data set. This ensures that Vicmap Imagery mosaics are equally as accurate in high relief terrain as they are on flat terrain. The spatial accuracy of the Vicmap Imagery mosaics is dependant on the accuracy of the Vicmap Transport - Roads network, the accuracy of Vicmap Elevation used in orthorectifications, and the precision with which control points are collected. Individual and average control point root mean square (RMS) errors for each component image are required to be less than or equal to one pixel, or thirty metres. This is usually achieved for all component images with most average control point RMS errors falling under fifteen metres. In general, ninety percent of all Vicmap Transport - Roads should fall within plus or minus 30 metres of Vicmap Imagery. 

Conceptual Consistency

Comments

Land cover features across the component images have generally been colour-balanced and matched to each other so that a consistent appearance is achieved across the State. The Vicmap Imagery mosaics have been enhanced to approximate true colour. However, they are still technically false colour representations. In general, forest and tree cover is represented in dark green, irrigated pastures and crops appear as light green, dry pasture and soils vary between red, brown and orange and water is represented as blue. 

Missing Data

Comments

Statewide coverage is achieved by mosaicing sixteen Landsat images. 

Excess Data