Understanding the physical characteristics of land is just as important as assessing the development of land. Before any site can be designed and ultimately developed, professionals need to first understand its elevation, slopes, drainage patterns and relationship with the surrounding terrain.
Traditional surveys can provide detailed information, but modern remote-sensing technologies can offer valuable terrain information across much larger areas.
One of these technologies is LiDAR (Light Detection and Ranging). Through laser measurements developers can better determine elevation as LiDAR can create highly detailed digital representations of the ground and surrounding features. This not only provides another source of information but also eases assessment of the physical characteristics and potential drawbacks of a site.
What Is LiDAR?
LiDAR is a remote-sensing technology that uses laser pulses to measure distances between a sensor, objects or different surfaces. The system sends out large numbers of laser pulses and records the time taken for those pulses to return. These measurements can then be used to calculate elevations and create visually detailed models of the surveyed area.
LiDAR can be collected using aircraft and other technologies, allowing large areas of land to be effectively mapped out.
The Environment Agency's LiDAR programme gives us detailed elevation data from across England, alongside Digital Terrain Models available at resolutions even within just 1 metre.
Evolving into a 3D Terrain Model
The measurements taken from LiDAR can be converted into digital elevation models.
An important type of which includes the Digital Terrain Model (DTM), represents the foundational terrain surface, which removes surface objects such as buildings and vegetation during processing. This makes the DTM especially useful for understanding the shape of the ground itself.
A Digital Surface Model (DSM) is different, it displays the elevation of the terrain together with objects on the surface including buildings or vegetation.
Slopes and Elevation
Terrain can have a significant influence on how land can be developed. A terrain model created from LiDAR can show differences in elevation across a site, which helps identify areas with steeper or flatter slopes.
This data can aid the early assessment of:
- Site and ground levels
- Ground gradient
- Changes in elevation
- Potential access routes
- Areas needing earthworks
- Relationships between different areas within a site
A three-dimensional representation can be used to make these differences easier to understand, rather than opting for a conventional flat map. However, it is important to note that LiDAR data should be treated as a key source of site information rather than a replacement for detailed site surveying.
Supporting Drainage and Flood Assessment
Terrain is closely connected to how water moves across land.
Elevation data can help spotlight low-lying areas, changes in ground level and any potential surface run off paths in the case of torrential rain. LiDAR is also widely used in flood modelling, as detailed topographic information is needed to accurately represent floodplains.
For development teams, this can help provide an earlier understanding of how the shape of a site might affect the quality of drainage, whilst also keeping flood-risk considerations into account.
Though planning mostly exceeds this level, needing more detailed hydraulic modelling and site-specific investigations which are still required before development decisions are made.
Identifying Landscape Features
LiDAR can reveal physical features that may have otherwise been difficult to spot from ordinary aerial imagery.
Changes in elevation can be shown via features such as embankments, depressions, earthworks or tracks within a terrain. These can be particularly useful when assessing larger, more rural sites where ground-level inspection of every part of the land may be difficult.
This technology therefore provides another way of understanding the physical character of a site before more detailed investigations take place.
Comparing Terrain with Existing Structures
When LiDAR data is available as both a DTM and DSM, development teams can more actively cross-examine the relationship between the ground level terrain and objects on its surface. For instance, the DTM can provide information about the ground level, whilst the DSM can show the heights of infrastructure and surrounding vegetation.
Comparing the two can help create a more complete three-dimensional understanding of the site. This distinction can also prove to be useful when considering how existing structures relate to slopes, surrounding land and potential development areas.
LiDAR and Development Design
Terrain information can influence early development design. For one, significant changes in elevation may potentially affect the positioning of infrasturcture such as buildings, roads as well as pedestrian routes.
A 3D terrain model allows different design options to be considered against the existing landform before detailed design work starts. However, this does not mean that LiDAR automatically determines the best design. Instead, it provides accurate physical information that designers, engineers and developers can use when evaluating different options.
Combining LiDAR with Other Data
LiDAR, as most things ,becomes more valuable when it is combined with other information rather than being separately analysed.
A development team could potentially consider terrain alongside:
- Planning designations
- Flood-risk potential
- Transport infrastructure
- Existing buildings
- Environmental constraints
- Land boundaries
- Proposed development layouts
This integration helps creates a more complete picture of the interaction between physical characteristics of a site with its wider development context. A steep area identified through LiDAR could be considered alongside access routes and proposed building locations to understand whether the terrain creates a potential design or engineering challenge.
LiDAR Across Large Areas
One of the big advantages of LiDAR is its ability to provide elevation information across extensive areas.
The Environment Agency's National LiDAR Programme provides elevation data covering England, with different surveys and resolutions available depending on the location and survey requirements. This means LiDAR can be useful not only for individual development sites but also for understanding wider terrain around potential development areas.
Developers can therefore examine how a site fits into its surrounding landscape before committing to more detailed investigations.
The Role of Enterprise Technology
For larger development organisations, LiDAR data can become part of a wider digital information environment.
Enterprise technology from Oracle Corporation can effectively support the integration of data across all operational, project and financial systems. This centralising method allows connection between terrain information with land records, planning data, project information and development costs.
Information about difficult terrain can now be considered alongside project budgets or design information, helping development teams understand how physical site conditions might affect wider project considerations.
Conclusion
LiDAR and 3D terrain mapping are making it easier to understand the physical characteristics of land before development begins. By measuring elevation and producing detailed terrain models, LiDAR can work alongside developers, helping to examine slopes, levels, drainage patterns and features within the landscape.
As land assessment becomes increasingly digital, LiDAR provides an important connection between geographic data and the physical reality of a development site.
Future articles will explore how satellite imagery can support large-scale land monitoring, how drone-based reality capture can create detailed digital representations of development sites, and how computer vision can analyse visual information from development environments.
