The Government of Jersey's Infrastructure and Environment Department have an in house specialised team of engineering surveyors which supports the Government's delivery of critical infrastructure projects, from:
- roadworks maintenance programmes
- public realm improvements
- drainage programmes
- coastal defence projects
- major projects such as the new hospital development
Topographic survey
A topographic survey, also known as a 'topo survey', is a specialised type of land survey that focuses on capturing the three dimensional features of the earth's surface, both natural and man made. The main objective of a topographic survey is to create an accurate representation of the terrain, including its:
- elevations
- depressions
- other physical attributes
Topographic surveys are essential for our construction projects, public realm planning, environmental management, transportation infrastructure and coastal development.
By providing detailed information about the site's characteristics, topographic surveys enable our engineers, architects, planners, and other stakeholders to make informed decisions, assess potential challenges, and design solutions that consider the unique attributes of the landscape.
Key benefits of topographic surveys
Topographic surveys offer several benefits that make them invaluable for our engineering activities. Some of the key benefits of a topographic survey are:
Informed decision making
| By providing a detailed representation of the terrain and its features, topographic surveys help us to make informed decisions related to site selection, project design, and resource allocation.
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Accurate project design
| Topographic surveys enable our engineers to develop designs that take into account the unique attributes of the landscape, ensuring that projects are tailored to the specific site conditions.
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Cost and time savings
| Identifying potential challenges and opportunities in the early stages of a project can lead to more efficient construction processes.
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Risk management
| Understanding the existing site conditions, such as slopes, drainage patterns, and soil characteristics, helps project teams identify potential risks and develop mitigation strategies to ensure the safety and stability of the project.
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Boundary verification
| While not their primary purpose, topographic surveys can also help verify property boundaries, easements, and rights-of-way, ensuring that projects do not encroach on neighbouring properties.
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Asset management
| Topographic surveys can serve as a valuable tool for asset management, helping government track changes our land holdings, monitor infrastructure conditions, and plan maintenance or improvement projects.
Topographic surveys offer government benefits that contribute to the success of our projects. By providing accurate, detailed information about the land surface and features, our surveys and surveyors enable informed decision-making, efficient project design, risk management, and ultimately leading to cost savings, time efficiencies, and sustainable project delivery. |
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What a surveyor does
During a topographic survey, surveyors collect data on a range of features, including:
- Elevations: The heights of various points on the earth's surface, typically expressed as a vertical distance above a reference point, such as mean sea level
- Contours: Lines connecting points of equal elevation, which help illustrate the shape and slope of the terrain on a two-dimensional map
- Natural Features: Elements such as streams, water bodies, woodland forests, hills, valleys, and rock formations
- Man-Made Features: Structures and facilities like buildings, roads, bridges, utility lines, fences, and walls
- Boundaries: Property lines, easements, and rights-of-way that define the legal limits and ownership of the land
Why do we need surveys
Topographic surveys provide the foundational data needed for accurate planning and design.
It is crucial to determine the appropriate level of information and accuracy before commencing any site work. Failing to survey specific assets or features can result in delays to the project and design works.
For example, if trees, level changes, or service covers are not indicated, this could adversely affect the foundation designs, drainage plans, or proposed building heights.
Therefore, it is important to conduct a thorough survey to avoid any potential hurdles and ensure a smooth and successful project implementation.
What techniques do we employ
To perform a topographic survey, our surveyors use a combination of advanced tools and techniques, such as total stations, GPS/GNSS receivers, levels, 3D laser scanners, and aerial surveying methods using drones.
The collected data is then processed, analysed, and presented in various formats, including topographic maps, digital terrain models (DTMs), and geographic information systems (GIS).
Total station survey
A total station survey is a type of surveying technique that uses a combination of electronic distance measurement (EDM) and electronic angle measurement (EAM) to accurately measure distance, angles, and elevation.
Total stations are advanced pieces of surveying equipment that combine a theodolite, EDM, and data collector all in one unit.
Total stations use a laser beam to measure distances to a target. By bouncing a laser beam off a prism or reflector, the total station can determine the distance from the unit to the target.
It can also measure the angle between the unit and the target using an electronic angle measurement system.
3D laser scanner
3D laser scanning or High Definition Surveying (HDS) allows you to quickly capture, visualise and pre-register data in the field, which can then be processed to deliver conventional 2D models and 3D digital models
The HDS system consists of a portable 3D laser scanner which supports standard surveying procedures. Any exposed surface can be remotely captured in minutes to form a dense and accurate 3D point cloud.
The amount of detail that the Laser Scanner obtains is a direct benefit to our teams as the scanners typically have a scan rate of 50,000 points per second.
This scanning method can cover a larger area in significantly less time and to greater detail than conventional survey techniques. The resulting data allows us to extract more as-built information than before.
GPS
Global Positioning System (GPS) is a satellite-based positioning system, which by virtue of its special characteristics has revolutionized surveying. Our in-house surveying team has a depth of experience when it comes to using GPS and with the use of Leica's hardware and software integrated systems we offer a solution to our projects which gives increased efficiency and cost savings.
Drone surveys
Drone surveys is our latest surveying technique to be employed in house by the surveying team, who are all qualified drone pilots with commercial pilot licences in line with Civil Aviation Authority (CAA) requirements.
How Drone surveys work
The surveys utilise photogrammetry point cloud techniques to map out the existing land and coastal area. The survey will use the 'Point Cloud' method, which creates a representation of an area, building or feature though a collection of data points which get plotted in 3D.
Millions of scan points will be recorded and combined to create an image of the defences and beach profile. When performing these surveys Islanders may see a drone flying above certain pre-designated areas to obtain geographic terrain and structure data which is then used to create a 3D terrain and structure model.
Benefits of drone surveys
Drones are suited for rapidly acquiring data from vantage points inaccessible to our survey team from the ground.
When surveying challenging terrain, drones make it no longer necessary for our teams to physically access and measure points in hazardous or difficult-to-reach locations which we have around the island, particularly coastal areas.
While traditional surveying methods require meticulous measurement, preparation, and planning, drones can capture comparable data in dramatically shorter timeframes.
When performing our surveying activities information collected by a drone will not be personal information, where personal information is considered as any information about an individual who is or can reasonably be identified. In addition, when post-processing the data recorded, should any personal information be collected then this will be removed from this processing stage, such that no personal information is retained.
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