The IKONOS satellite orbits at 680 km above the earth and travels at 7 km per second while capturing imagery fine enough to distinguish cars, trees and powerline towers. Geoimage, one of Australia’s premier satellite imagery processing and services provider, and Raytheon Australia, the market leader for satellite imagery throughout Australasia, have partnered to provide processed and GIS-ready IKONOS imagery to clients in Australia.

The IKONOS satellite can capture imagery with 4 multi-spectral bands at a resolution of 1 m, allowing natural colour, and colour-infrared imagery to be captured at the same time. The satellite can capture up to six adjacent and overlapping swathes in the same overpass, potentially capturing an area 66 km wide in one day. The imagery is purchased on a square km basis, which has the advantage of allowing users to only purchase their exact area of interest.

Geoimage was approached by Mipela, the GIS contractor to Enertrade, with the task of providing high resolution, but cost-effective, imagery that could be used as a backdrop in a GIS for the North Queensland Gas Pipeline (NQGP).

Enertrade required the imagery for the planning and construction phase of the pipeline. The imagery was to be provided as a natural colour, geometrically accurate, seamless mosaic with a one metre pixel size, covering the entire length of the pipeline route, with a buffer of 2.5 km either side of the proposed line.

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The IKONOS archive provided imagery of sufficient resolution at the cheapest price over the entire length of the proposed route, except for a small section near Townsville where the imagery was cloud-affected. Therefore, a total of 1815 square km of archive IKONOS and 166 square km of new capture IKONOS imagery was ordered. An accurate digital elevation model (DEM) was required for the orthorectification of the imagery and was provided by Geoimage in the form of a 15 m DEM produced from the ASTER satellite’s in-track stereo imagery.

After delivery, Geoimage produced 1:50,000 scale hardcopy prints of the raw IKONOS imagery for accurate ground control collection. Once orthorectified and accurate to within a metre, the IKONOS images were colour matched and joined to produce a seamless mosaic along the pipeline route. This colour-balanced imagery was tiled for ease of use and supplied to Enertrade as both a load-and-go GIS layer and as uncompressed image files for remote sensing vegetation analysis.

The purchase of the IKONOS satellite imagery has allowed the establishment of an archive of cloud-free imagery covering the whole project area. This enabled the environmental baseline to be established prior to the commencement of construction. Little had changed in the past 10 years because the area is remote so using archive imagery that was 1-2 years old did not pose a problem to the Enertrade and Mipela team.

This high-resolution GIS dataset was used for route selection; risk assessment and pipeline design; and for alignment sheet generation. Since work could be completed from the office, a reduction in the number of site visits was also achieved. Access issues associated with landholder, cultural heritage and environmental management were also addressed and the cost-effectiveness of using archive imagery when compared to other methods of image acquisition proved to be an added bonus.