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Photogrammetry: a rapidly evolving aerial survey methodology

Updated: Jan 31

Using specialist aerial survey equipment, photogrammetry enables rapid data capture of hard to access areas.


The equipment can be fitted to tripods and masts or attached to Unmanned Aerial Vehicles (UAV). As a methodology, photogrammetry is as old as modern photography. Experiencing a decline in its use with the development of laser scanning, photogrammetry as a technique in Aerial Surveys, has ‘taken to the skies’ once again with the increasing popularity of UAV's, and improvements in associated software.


Aerial Survey data

Aerial Survey data is collected by capturing overlapping digital images, which are combined to generate the final deliverable. Modern photogrammetry software analyses parallel images, convergent images, as well as those which are oblique (both horizontal and vertical). Current software available on the market even allows for the use of oblique images from flights that circle the subject as opposed to a more standard aerial mapping flight path of overlapping swaths.


Using the latest UAV technology and mobile masts, SUMO can survey site areas which may be impractical or costly to survey with more traditional survey methods. The advantages of aerial surveys include:


  • Reduced costs

  • Less requirement for access to areas of the site with restricted access by foot

  • Reduced time needed to survey the site

  • Increased reaction time

  • The best value solution when combined with the flexibility of conventional survey methods


Historic Building Recording

It is however imperative to employ skilled and qualified staff when ordering an Aerial Survey, who should hold the necessary licenses and permissions for commercial operation, together with appropriate insurance. All flights carried out by SUMO are undertaken by fully qualified pilots, within the CAA framework and with appropriate risk assessments carried out. SUMO also holds £x insurance cover. Where required, SUMO will also liaise with the local police and obtain ATC (Air Traffic Control) clearances.

SUMO’s Aerial Survey division provides services for purposes which range from commercial, industrial and structural to environmental, conservation and heritage. Photogrammetry as a method of data collection is often employed throughout our full range of Aerial Surveys which includes:


  • Landscape Surveys

  • Volumetric and Quarry Surveys

  • Roof Inspection Surveys

  • Aerial Archaeology Surveys

  • Historic Building Recording




Above: The example above shows a 3D model created using photogrammetry data collected by SUMO Aerial-Cam. The data was obtained from the Eastham bridge as a part of efforts to plan repair work after its collapse. The viewing software Sketchfab (above) is one of many ways that clients can view the photogrammetry data. The benefit of this free 3D viewing software is that the client can manoeuvre the model by themselves, with the option to magnify areas of the model for closer inspection.




Photogrammetry

So why use photogrammetry, when the widespread use of laser scanning has made significant developments regarding surveying hard to reach areas? In short, there are still areas that remain extremely difficult, if not impossible to access, without the use of scaffolding or elevated work platforms. Confined roofs, high buildings, as well as vast landscapes are a few examples of these hard to reach areas, where photogrammetry would be a more appropriate and cost-effective solution.

What’s more, whilst there are benefits and limitations to Aerial Survey methodologies as well as more conventional methods such as Laser Scanning, they do integrate easily to create a suitable combined approach. Below is an example of this combined survey approach in action at the Hampstead Parish Church…

To rapidly capture the elevations of the Church, a Laser Scanning Survey was initially undertaken. However, because of the design of the building and the lay of the land, it was quickly discovered that the roof structure was almost completely obscured. To overcome this, a UAV with attached photogrammetry equipment was then flown across the site to capture each side of the church. In order to keep the drone in sight at all times and to capture all of the data necessary, the Aerial Survey was undertaken in separate flights from different positions, as it was essential to get good coverage of the site to allow for the matching of the dataset collected by the UAV to the dataset collected using the laser scanner.

Furthermore, several common points between the laser scan and photogrammetry data were picked, so that the aerial data could be registered. Next, the UAV photogrammetry data was converted into pointcloud data and integrated with the pointcloud data collected by the laser scanner. This process and approach to surveying the Church allowed for a comprehensive data set and deliverable for the client.


Detailed roof plan and 2D elevations

Above: A land survey, detailed roof plan and 2D elevations of the church were provided to the church.


3D elevations

Photogrammetry is also often used for detailed historical recording and orthophotos, with textured meshes being a new deliverable available to clients. The quality and the actual colours captured using the technique provide extra information to clients and is especially useful for conservation specialists. The additional level of detail obtained through photogrammetry would be hard to achieve from other methods such as laser scanning alone.


Aerial photography taken at Rochester Cathedral

Above: Aerial photography taken at Rochester Cathedral by SUMO Aerial-Cam as a part of a Historic Building Recording Survey and Roof Inspection Survey. Photographs such as this are often used to create accurate 3D models, which are created using both advanced photogrammetry software as well as modelling tools such as Revit.


In conclusion, photogrammetry is very much an emerging method of surveying and capturing information, with hardware and software developing in leaps and bounds. This fast growth is also fuelled by the increasing popularity and availability of UAV’s for commercial use. Whilst already working with the latest technology, SUMO is eagerly awaiting and ready to embrace the next generation of photogrammetric solutions, which are no doubt waiting in the wings for this very modern surveying technique.


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