Aurecon developed an integrated approach to Obstacle Limitation Surface (OLS) Surveys through the Australian Government Department of Defence’s Airport Technical Inspection (ATI) Project, significantly reducing the risk associated with obstacles around airfields that may not have previously been documented.
The project, which ran between 2015 and 2020, was a comprehensive approach that combined LiDAR (Light Detection and Ranging Arial Survey) Survey from an aircraft with conventional methods to identify obstacles and document these to ensure safe take-off and landing.
With new airfields an OLS survey will be done before the airfield is built, ensuring minimal obstacles in the take-off and approach paths, however, structures are often added afterwards therefore impacting runway safety.
The integrated LIDAR and ground survey focused on Type A Obstacle Charts for Take-off assessments and Obstacle Limitation Surface Surveys, which take into account take-off, approach, transitional, inner horizontal, conical and outer horizontal surfaces.
Defence has moved to adopt Civil Aviation Safety Authority Manual of Standards 139 (MOS139) in full and reports the majority of its larger airfields to this standard. Prior to this project, Defence had many OLS assessments and Type A Charts that were several years old.
Our integrated technique allowed for a far more complete and efficient analysis of potential obstructions in OLS areas by providing a point cloud as well as high resolution imagery from the aerial LiDAR survey combined with conventional ground survey data.
This combined digital solution reduces the time spent on the ground for the survey team to determine obstacles across large assessment areas. The two-method approach also reduces the chance that obstructions could be missed, as both independent methods are run separately and results then consolidated.
Airport Technical Inspections (ATI) are essential to ensure the safety of airfields and runway compliance. Every airfield needs to have an Obstacle Limitation Survey completed as part of the ATI. Defence also wanted to bring its larger Tier 1 and 2 airfields into line with MOS139 standards.
Aurecon’s Spatial Surveying team surveyed 21 Defence airfields across Australia. The data captured was used to compile Type A and B International Civil Aviation Obstacle Charts used by flight planners and pilots to determine the maximum performance for aircraft at take-off, considering existing or new obstructions within the take-off area or splay on the nominated runways.
Obstacles could include things such as manmade towers; antennas and buildings; moving obstacles such as vehicles and natural features such as vegetation.
Any obstacles identified needed to be positively identified and classed as one of the following:
Using an integrated approach with LiDAR and ground surveying meant Aurecon could complete a digital capture in the OLS areas, which made identification easier and significantly reduced the chance of missing obstructions when compared to using just traditional survey methods.
Our OLS report advised Defence on what it could do to address obstacles that were found. With a comprehensive survey dataset, this task was made significantly easier and gave our airfield engineers confidence in making decisions and providing additional engineering support on items such as assessing runway strip gradients.
With the large amount of data from both methods we needed to deploy an efficient workflow that could deal with the volume, which on average was 3-6GB per site.
The initial project was completed over four years but extended to five due to additional aerial LiDAR work that was implemented.
The combined survey technique proved so successful that it has been deployed at Defence airfields outside the immediate program and has the ability to be applied at capital city airports as well as smaller city and regional airports.
Traditionally, for this type of project, only a ground survey would be completed. However, our team combined traditional survey methods with a LiDAR aerial survey taking an on and above ground approach and providing extra value-added data and imagery to further de-risk the project and provide extra confidence that nothing has been missed.
Geographic Information Systems (GIS) software was used to help analyse the massive amount of data collected.
To capture the LiDAR, we subcontracted AAM Group to conduct the aerial survey over an approximately 3km wide by 32km long corridor based on the runway as the centre. The whole corridor was laser captured and the information analysed against the OLS surfaces to identify any breaches.
The ground survey team then captured detailed ground survey within the immediate approach and take-off surface areas on the airfield. These high risk areas were examined for smaller or slimmer obstacles such as antennas that could be missed by the LiDAR.
Completing this level of survey by only using traditional ground survey would have been incredibly time consuming and almost impossible because of difficulties with access and permissions for certain areas. ArcGIS was used to run the analysis, comparing all the survey data against the OLS models imported from AutoCAD.
As part of this process, a custom script was developed to automate most of the analysis process and calculate the required outputs. The script exported the obstacles to a table and text format as specified by Defence. The approach is also adaptable to capital city airports along with other smaller city and regional airports.
Our combined digital solution, including LiDAR and GIS, reduced the time spent on the ground for the survey team to determine obstructions. Less time spent on the ground meant fewer disruptions at the airfields and reduced time needed on the live runways. This was even more important at the larger bases where there is much more air traffic, and is directly relevant to capital city and larger regional airports.
Limiting the amount of time, a survey team is required on or near a live runway greatly reduces the health and safety risks for both Aurecon and Defence.
Many sites, particularly in the Northern Territory and Northern Australia, encounter weather challenges, so we had to plan for and respond to data capture opportunities quickly.
Whilst the LiDAR can be flown in most weather conditions, image quality can be affected by cloud cover.
Our team also worked in and around Defence movements, such as Talisman Sabre and Pitch Black, to ensure ongoing operations and security were not compromised.
Ultimately, this approach provided a large amount of surrounding survey as well as aerial imagery that can be used by Defence for a range of purposes and provided a higher quality assessment of obstructions that can be easily understood, assessed and actioned upon for safer airfields.
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