Crucial Services were commissioned to carry out a topographical survey in Newtown, Powys in the area of Gas Street. Given the nature of the area, sections were needed as part of the survey to allow the potential design to be related back to the landscape and the setting of that part of Newtown. This presented several problems for a potential survey. Principal amongst those was the visibility of the surrounding area from the site and street level. A key need was heights on adjacent or overlooking properties and ground levels by those buildings and other features.
This presented several problems in terms of access to measure the required information. A traditional land survey could have measured these points but it would have required several extra control stations to measure those points using reflectorless technology in the disparate locations needed. Terrestrial laser 3d laser scanning would have measured the majority of these points with less effort and in a more comprehensive way but will have still needed a line of site to see all the points needed. Trees, tall walls and other obstructions obscured the required points from street level. However, our recommended approach for this project was for a photogrammetric land survey with a drone.
As a remote sensing method, a drone land survey using photogrammetry doesn’t involve direct contact with the points to be measured. A drone survey is accurate and comparable to a traditional land survey and met the client’s brief.
Quicker, fast, safer with a drone survey
A comparison of survey times using various methods on this project:
- A traditional survey would have taken the best part of the day to gather the data needed.
- Terrestrial 3d laser scanning would have taken a morning to measure and still would have had gaps in the data.
- The entire drone operation was concluded within an hour. The operation included set up, pre-flight checks, the flight, post-flight checks, surveying ground control and a check survey.
Many more data points were collected using photogrammetry – far more than would be possible with a ground-based land survey. With a 3d textured model of the survey area and more surrounding context, the usefulness of the survey for the client in terms of the setting for the planning application is vastly improved deliverables. The extra information helps the designers to make more informed decisions for the benefit of their clients. Thus improving the quality of the application and the design, and improving the chances of a planning application being passed.
Sparse point cloud
Classified point cloud
Textured 3d model (extract)
This drone mapping survey was flown in the small hours of the morning to avoid traffic and pedestrians during the drone operation. The mission used safety marshalls to spot ground-based hazards when vehicles or people entered the survey area. The drone flight was paused while traffic passed without overflight by the drone. This allowed the remote pilot to concentrate on the airspace and the drone flight.
Post drone flight check survey to verify the accuracy with an assistant surveyor/safety marshal. A ground control point for the drone survey can also be seen (bottom right)
It is important for us to follow a robust methodology when we undertake a drone survey. This is no different to the approach followed when undertaking a traditional ground survey by establishing the correct control framework for the project. For a drone survey, we also need to measure a check survey to reference points. This helps us ensure that our survey is accurate in a local, relative sense and in absolute terms when comparing other data sets like flood levels or older surveys.
The model has 221.4 M triangles and is 1.62 Gigapixels in size
The 3d textured model of the planning application area
If you would like to find out more about how a drone survey can help you gain planning permission then please feel free to contact us.