Demand for high-resolution imagery is booming in Australia. Through the New South Wales Land and Property Information (LPI) group’s Spatial Information eXchange (SIX), users in government, survey, land valuation and other applications increasingly access detailed orthorectified digital imagery and rich digital elevation datasets for critical planning and decision-making operations. To capture some of this information, LPI uses its own equipment, including a Leica ADS40 airborne digital sensor and Leica ALS50 airborne laser scanner. But forward-thinking programs with aggressive goals make it impractical for the agency to work alone. Within the last several years, the seemingly insatiable appetite for high-resolution imagery has allowed LPI to create new opportunities in the private sector by outsourcing key projects.
In 2012, LPI contracted the Australian land, engineering and aerial survey provider Vekta to capture and supply 10-centimeter GSD RGB imagery with a spatial accuracy of +/-0.25 meter RMSE of the entire metropolitan and surrounding areas of Sydney, Newcastle and Wollongong, covering an area of approximately 14,000 square kilometers. The area extends far enough west to include the rugged ranges of the Blue Mountains.
This is the largest high-resolution imagery project undertaken over the Sydney metropolitan area to date and also one of the most complex. Most of the project area falls within the controlled airspace of Kingsford Smith Airport, one of the busiest in Australia. Some Australian airspace restricts access to lower altitudes for prolonged capture, so the imagery must be acquired at high altitudes. In addition, it must be captured with a minimum solar angle of 50 degrees to minimize shadow effects and solar flare reflections from water bodies. “Due to the restrictions of sun angle, weather and air traffic control, we needed [to use] a camera that was reliable and efficient with its capture,” says Vekta’s Director Leo Watts.
Aerial camera technology has advanced rapidly over the last several years. Vekta, which has provided spatial and surveying solutions for more than six decades, has used a variety of different cameras to capture imagery, most recently relying on several large-format film-based cameras and a medium-format digital camera. In 2011, the company began looking for a new camera that would improve its ability to handle large projects.
The company was drawn to the VisionMap A3 digital camera, which has a footprint of 60,000 pixels across the flight track, the ability to collect thousands of square kilometers each day in high resolution, a fully automatic processing end-to-end workflow and the ability to provide aerotriangulation, digital surface models, orthophotos, stereo models and oblique georeferenced imagery with a fast turnaround time. “VisionMap A3 demonstrated not only extraordinary imagery collection efficiency and end-to-end automatic workflow, but it is also very easy to operate in air and can be easily integrated into our current processing environment,” said Malcolm McCoy, managing director of Vekta, when the decision was made in September 2011 to move forward with the purchase.
Through a combination of training provided by VisionMap and internal training, Vekta began learning how to integrate the new system into its process to create an efficient workflow with large volumes of data. By the time Vekta was awarded the project through LPI, the firm was confident in its camera selection. “The A3 camera was the most suitable large format digital aerial survey camera to undertake such a project,” Watts says.
Working within the time restrictions imposed by the solar angles, Vekta began collecting the high-resolution imagery across Australia’s southeast coastline. The project requires more than 220 flight lines totaling more than 10,000 line kilometers. To optimize collection efficiency, the team alternates the VisionMap A3 camera between a Cessna 402B twin engine and Cessna 206 single engine aircraft. When one aircraft needs to land for maintenance and refueling, the other aircraft is sent out.
The camera’s long focal length allows the team to operate at an altitude of 10,000 feet, thereby avoiding conflicts with the busy Sydney airspace. According to Watts, the combination of wide image swaths and higher flying heights maximizes the chance of successful capture. “Undertaking this project with another large format digital sensor would be very challenging due to the competition for airspace and restriction on access and operational flying heights imposed by air traffic control,” he says.
The captured imagery is quickly processed in the camera’s LightSpeed digital processing system, which automatically does the work of several teams. The system processes hundreds to thousands of kilometers of imagery per day, producing high-end photogrammetric products tailored to meet the specific formatting and quality requirements of the client. “There is no point in having rapid capture if the imagery can’t be supplied in a similar fashion,” says Watts. “LightSpeed processes the imagery rapidly and at a high standard.”
As a final QA/QC step, the tiled digital orthophotos are manually checked for imperfections and compliance with the specification. “Establishing consistent and efficient checking processes is a key challenge for any significant image acquisition project where spatially accurate and radiometrically consistent imagery is the output,” explains Watts.
The project is expected to be completed by the end of the first quarter of 2013. The resulting imagery will assist in traffic planning and management, town planning application assessment, urban monitoring, building application auditing and compliance, and environmental monitoring, along with a host of other applications.
For LPI, the project is key to achieving its goal of having digital aerial imagery coverage across most of New South Wales in 2013. For Vekta, the project confirms that the new camera investment was a wise decision. “Compared to other systems, we believe the A3 provides the most efficient end-to-end solution from capture to delivery for high resolution orthophotos over large areas, particularly urban areas that have flying restrictions in their airspace,” Watts says.
“There has been a significant growth in Australia for the demand of high resolution imagery,” he adds. “The A3 gives us the ability to grow our business by being a major supplier in this market.”
For more information about Vekta, visitwww.vekta.net.au. Additional information about the VisionMap A3 camera can be found atwww.visionmap.com.