There are three major steps that an engineer or GIS specialist will need to complete in order to proceed with a project requiring specific terrain data and imagery. Firstly, it is necessary to consult with a survey and mapping adviser about the project scope, including feasibility, pipeline route selection, design and construction. The next step is to provide the adviser with a digital file of the project extent so the site characteristics can be assessed. Finally, it is important to let the survey and mapping adviser report on what existing data may be available or which technology may be the best tool for the project.

This is important because with the advent of high resolution satellites, digital aerial cameras and airborne LiDAR, a range of terrain and image data sources exist to generate the products each project requires. For large projects, aerial survey by LiDAR or camera permits data capture and mapping at a pace more rapid than possible using field surveyors – especially given the current high demand on their services. Datasets derived from aerial survey assist the project, leaving the field surveyors to work in the accessible areas undertaking the higher accuracy work.

The size of some projects and the related ground access issues, immediately dictate that an aerial solution supported by field surveyors is the best way to proceed. The aerial survey tool best deployed depends on many factors, some of them listed in the table on page 90. For example, on some project sites the terrain, vegetation density and/or weather may dictate that a LiDAR solution would supply a more timely and accurate result. In other cases, terrain models derived from a camera will satisfy the project’s requirements.

Airborne LiDAR – Light Detection and Ranging, also known as Airborne Laser Scanning – is an outstanding application for pipeline corridors. Its success has been proven on numerous major corridors, most recently the Western Corridor in Southeast Queensland and the Victorian Spatial Excellence Award-winning Wimmera Mallee Pipeline Project (WMPP).

LiDAR is a technology which has been around since the 1990s. AAM Surveys was the first to introduce this technology to the broad Australian market. LiDAR sensors emit and measure received light. Each laser return is recorded and the time taken is measured to calculate the vertical and horizontal height of that strike along with information about the intensity of the strike.

LiDAR height data is complemented by positioning technologies to ensure a high quality and highly accurate terrain model is derived for engineering purposes. Positioning technologies such as direct airborne georeferencing units and airborne GPS, accompany the LiDAR sensor in flight allowing the positional accuracy to be achieved. For even higher accuracy products, this airborne data is further complemented with a GPS base station and a number of reference and check points taken on the ground.

However, it is important to note that not all LiDAR sensors are equal. Some have medium format digital cameras attached for simultaneous image capture. They are supported by a range of different software packages and algorithms for product generation. In addition, some digital photogrammetric software packages will produce a superior result from automatic terrain generation.

The key facts to be aware of include:

* Data collection sensors of LiDAR and digital cameras vary in capability * Data processing software packages vary in capability * Expertise of the data processing analysts is a vital input * Project site characteristics and deliverables determine the best tool for the job

Therefore, the terrain model quality is related to the type of technology deployed given the project characteristics and the skills, software and processes of the company.

It is important to note that the major conclusion of the discussion of the APIA Convention was that LiDAR is not necessarily a black box technology for every application. A successful result can be often obtained with the use of a suite of complementary 3D technologies. Ultimately, a pipeline engineer with a geospatial partner is a formidable combination in ensuring that the best mapping and modelling datasets are used for each individual project.