3D modelling above and below ground

Access to a growing volume of data and an enviable toolkit is helping surveyors to compile an accurate picture of development sites – both below and above ground. By Martin Berry

One of the principal challenges of urban design is to ensure that any new scheme ‘fits’ with our inherited legacy. To some, the emphasis on the concept of ‘fit’ will be biased towards physical appearance, how the physical attributes can aesthetically enhance or sympathise with that which already exists. To others, including the humble surveyor, the concept of ‘fit’ has more quantitative connotations. Thankfully this latter genus benefits from an increasing volume of data and an enviable toolkit – the real challenge is making sense of it all and ensuring that the right mix is employed in making that informed decision.As premium urban space becomes increasingly rare and valuable, it is worth considering just how congested things are below our roads and footways. Several centuries of infrastructure, from sewerage networks to high bandwidth fibre-optic data, sprawls beneath our feet. These networks are taken for granted but, without them, our cities would cease to function. The passage of time, the implementation of different systems and the churn of administrators are but a few of the factors that contribute to our incomplete knowledge of exactly where and how these subterranean networks reside. Small print on the various owners’ plant maps tends to disclaim any responsibility for accuracy and currency of such.

Clearly every design needs a starting point and an end vision. As surveyors, we strive to provide the most accurate picture of the starting point, both above and below ground. The topographic survey provides a clear definition of the space in which the designer has to work. A measured building survey provides an accurate model of existing Subsurface imaging with ground penetrating radarLaser scanning: providing accurate 3D modelsstructures – physical connectivity, access ways and right to light data, all of which help with the planning approval process. Underground infrastructure mapping helps to avoid the unmoveable, to quantify the moveable and to facilitate new scheme connectivity.

As a surveying practice, we were recently retained to provide quality control services to an ongoing urban development. It was only during the piling process that it became clear that the design team had not fully considered the information within the topographic survey – several of the proposed pile positions fell within the adjacent petrol station. Furthermore, it was only after the development of a rather intricate and expensive pump drainage scheme that the team discovered existing adjacent capacity within a 50-year-old gravity sewer. In this highly illustrative case, it was simply the starting point that lacked definition. Our primary recommendation for future projects was to ensure a comprehensive, accurate and integrated survey of the existing site; both above and below ground.

There have been great technological advances in the surveying equipment available over the last 10 years. Terrestrial laser scanning and close range photogrammetry have revolutionised our ability to 3D model the above ground environment. Ground penetrating radar and associated radio location techniques have allowed us to ‘peer’ underground like never before. The availability of spatial data increases at an unstoppable pace. Computing power allows us to analyse and communicate data at amazing speed. Integration of these various data and techniques can provide us with the complete stating point picture. Inherent respect for accuracy in the data acquisition and management process ideally positions the surveyor in responding to this challenge.

Martin Berry is the director of Landscope Engineering: www.land-scope.com

contents: Technology, space & place