Input Dataset

NSW Town Orthorectified Aerial Imagery

Theme

Imagery

Jurisdiction

NSW

Custodian

This imagery data series is a collection of mosaics covering NSW’s towns or cities in NSW. It was created by ortho-rectifying, colour matching and joining overlapping image strips captured with multiple flight lines over the project area using a Leica ADS40 or ADS80 airborne digital sensor. This imagery can be obtained as a true colour RGB or BGRN image using the Red, Green, Blue or Near Infra Read More »

Metadata Address

https://sdi.nsw.gov.au/catalog/search/resource/details.page?uuid=%7BDF0F2422-4E2…

Dataset Purpose

This product has been produced to identify visible features and terrain for Local Government and Land and Property Information (LPI)’s standard mapping programs. This product is also used on a whole of government basis as a visible record of the landscape at a given point in time, allowing for comparative analysis to be carried out over different epochs.

Funding Support

Access Mechanisms

Online, Email, FTP, in shop, post.

Access Format

{ECW,Jpeg2000}

Dataset Lineage

LPI’s imagery has been captured using an ADS sensor (ADS40 or ADS80 as specified in each mosaic) and created using a documented process. The imagery capture program initially started in 2007 with ADS40 sensor. The sensor was upgraded to ADS80 in 2012. Depending on the processing and surface model used, positional accuracy of each image varies. The capture date, flight line information of each Read More » image can be found in respective individual metadata. The image capture, processing and delivery are consistent with well accepted digital image processing techniques (Leica Geosystems, 2009; 2010);1) A flight plan is created over the applicable mapping area, ensuring that the correct ground sampling distance (GSD) and run overlaps are maintained. The project area is then flown using the flight plan. 2) Raw imagery from the flight is downloaded from the sensor’s mass memory unit along with related global navigation satellite system (GNSS) data and inertial measurement unit (IMU) data. The downloaded raw image strips are geo-referenced using the associated GNSS and IMU data as well as base station or precise point positioning data. This geo-referenced imagery is referred to as level 0 imagery. 3) As the imagery data is captured at 12bits/band (4096 brightness values per band) and processed to 8bits/band (256 brightness values per band), a colour profile is created for the imagery by stretching and balancing the colour values to visually match the colours of features on the ground. This colour profile is then used in the subsequent processing levels of imagery for the project area. 4) Aerial triangulation software is used to run an automatic point measuring process. This process finds common image points on overlapping image strips. These points, along with surveyed control points and virtual photo centres (orientation fixes), are used by the aerial triangulation process to self-calibrate the sensor and improve the geo-referencing accuracy of the image strips. 5) Ortho-rectified imagery (referred to as level 2 imagery) is created by rectifying the image strips to a digital surface model of the project area. Colour difference between overlapping image strips are autocorrected to balance the colours across the entire project area. 6) The image strips of adjacent flight-lines are joined together at seam-lines along zones of similar contrast and colour and “feathering” is used to minimise any differences. As such, neighbouring pixels along these joins will have been captured at different times, which should be taken into account if this product is used for temporal analysis. To establish the location of these joins, a seam-line dataset is available for this mosaic upon request. 7) The image strips are joined and extracted into map partition modules. At this stage, the modules are Geo-TIFF files containing coordinate information, which is also stored in accompanying ERS files. These modules are combined and compressed into an .ecw file. A target compression ratio of 10:1 or 5:1 is used to create the ECW file with negligible pixel level change. LPI digital information is stored and processed within data centres certified to the ISO/IEC 27001 standard for Information Security Management in accordance with the Privacy and Personal Information Protection Act 1998, the Privacy Code of Practice (General) 2003, the Privacy and Personal Information Protection Regulation 2005 and the State Records Act 1998. « Less

Access and Licensing

Creative Commons Attribution 3.0

Identified Mandate

Yes

Content Source

National datasets

Very High Resolution (<2.5 m) Very Low Temporal Coverage (>annual)

The Location Information Knowledge Platform

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