Levelling applications
Contents |
[edit] Introduction
In surveying, levelling is a process of determining the height of one point (or level) relative to another. It is used in surveying to establish the elevation of a point relative to a datum or to establish a point at a given elevation relative to a datum. Several different surveying instruments can be used for levelling, all of which are loosely referred to as ‘levels’, for example, a spirit level.
Different types of levelling include:
[edit] Fly levelling
Fly levelling is a quick way of establishing a new temporary benchmark. The benchmark will help with the calculation of reduced levels. A temporary benchmark is usually used on smaller construction projects. On larger projects, levels will be linked to the Ordnance Survey Benchmarks.
Fly levelling is used for transferring levels and the only readings required are the backsight and foresight recordings. The intermediate sight readings are not used but the distance between readings should not exceed 50m. Fly levelling can be helpful when the benchmark is very far from the work station. In such a case, a temporary benchmark is located at the work station which is based on the original benchmark. It is not highly precise and is used for determining approximate levels only.
[edit] Whole circle bearings
Whole circle bearings refer to angles measured in a clockwise direction from north to establish levels. In whole circle bearing, the value of the bearing will vary from 0° to 360°. The angle between the north line to the survey line must be measured to establish the whole circle bearing. Co-ordinates are used in the calculations for whole circle bearings. The seconds, minutes and degrees of known points are used and deducted from each other to calculate the unknown angles’ co-ordinates.
[edit] Traverse types
Traverse levelling is the measure of the lengths and directions of a series of straight lines connecting a series of points. The straight lines are called traverse legs, and points are called a traverse station.
There are different types of traverse levelling applications:
- Open traverse - Has a different start and endpoint. It begins at a point of known control and ends at a station whose relative position is known only by computations.
- Closed traverse - Has the same start and endpoint.
- Directional travers - Extends directional control only. This type of traverse can either be open or closed.
See also: Levelling in surveying.
[edit] Related articles on Designing Buildings Wiki
- Building survey.
- Condition survey.
- How to layout a building.
- Land surveying.
- Laser scanning.
- Level.
- Levelling in surveying.
- Measurement of existing buildings.
- Robotic total station.
- Site surveys.
- Surveying instruments.
- Surveyor.
- Verticality.
[edit] External references
BTEC National Construction Student Book - Pearson
Featured articles and news
Quality Planning for Micro and Small to Medium Sized Enterprises
A CIOB Academy Technical Information sheet.
A briefing on fall protection systems for designers
A legal requirement and an ethical must.
CIOB Ireland launches manifesto for 2024 General Election
A vision for a sustainable, high-quality built environment that benefits all members of society.
Local leaders gain new powers to support local high streets
High Street Rental Auctions to be introduced from December.
Infrastructure sector posts second gain for October
With a boost for housebuilder and commercial developer contract awards.
Sustainable construction design teams survey
Shaping the Future of Sustainable Design: Your Voice Matters.
COP29; impacts of construction and updates
Amid criticism, open letters and calls for reform.
The properties of conservation rooflights
Things to consider when choosing the right product.
Adapting to meet changing needs.
London Build: A festival of construction
Co-located with the London Build Fire & Security Expo.
Tasked with locating groups of 10,000 homes with opportunity.
Delivering radical reform in the UK energy market
What are the benefits, barriers and underlying principles.
Information Management Initiative IMI
Building sector-transforming capabilities in emerging technologies.
Recent study of UK households reveals chilling home truths
Poor insulation, EPC knowledge and lack of understanding as to what retrofit might offer.
Embodied Carbon in the Built Environment
Overview, regulations, detail calculations and much more.
Why the construction sector must embrace workplace mental health support
Let’s talk; more importantly now, than ever.
Ensuring the trustworthiness of AI systems
A key growth area, including impacts for construction.