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Photogrammetry: a very modern solution

Updated: Jan 31

Photogrammetric Surveys enable rapid data capture using specialist cameras, either fitted to Unmanned Aerial Vehicles (UAV), or attached to tripods and masts. Photogrammetry as a methodology is as old as modern photography and whilst its use declined with the development of laser scanning, in recent years with the rising popularity of UAV's and improvements in associated software, photogrammetry has ‘taken off again’.


Overlapping digital images are recorded, which allow the collected survey data to be combined. Modern photogrammetry software can analyse oblique (both horizontal and vertical) and convergent images, as well as parallel images. The current software even permits the use of oblique images from flights that circle the subject, rather than flying in the more typical overlapping swaths used for aerial mapping.


SUMO uses the latest technology including UAV’s and mobile masts to survey areas which may be impractical or costly to survey with conventional technology. The advantages of aerial surveys include reduced costs, increased reaction time and best value solutions when combined with the flexibility of conventional methods.


Photogrammetry

It's important when providing Aerial Surveys to have skilled and qualified staff, as well as the necessary licenses and permissions to undertake such surveys. Our pilots are fully qualified to fly UAV's and all flights carried out by SUMO will be conducted within the CAA framework with appropriate risk assessments carried out. ATC (Air Traffic Control) clearances will also be obtained where required and this also extends to liaising with the local police.


SUMO’s photogrammetric and aerial services include environmental, conservation and heritage surveys, commercial, industrial and structural inspection. All of these have outputs including photography, photogrammetry and video as well as Pointclouds and meshes.


Typical applications of the type of the work that SUMO conducts include:


  • Historic Building Recording - A photogrammetric survey of historic structures, producing 3D models, elevation orthophotographs (rectified photography) and 2D stone by stone detailed line drawings.

  • Roof Inspection - Photographic, photogrammetric and/or video inspections of roofs and inaccessible areas of structures. This eliminates the extra costs associated with scaffolding as well as the risks to personnel working at height.

  • Topographic Survey - Digital terrain models, digital surface models orthorectified (orthophotos) and mapping of large areas.

  • Broadcast Quality Filming - Video production with amazing birds-eye views.

  • Stripped Area Survey - Rapidly records the detail of features of large areas in photo-textured mapping.


Above: The example above shows a 3D model created using photogrammetry data collected by SUMO Aerial-Cam.


The widespread use of laser scanning for surveying the built environment has made a significant step in surveying those otherwise hard to reach areas. Yet there are still areas that remain inaccessible without the use of costly scaffolding and elevating work platforms. These include confined roofs and high buildings, as well as large landscapes where photogrammetry would be an appropriate and cost-effective solution. In fact, combining Aerial and Laser scanning technologies can often be the best solution. Below is an example of a combined survey approach at the Hampstead Parish Church.


Terrestrial 3D laser scanning was initially undertaken at Hampstead Parish Church to quickly capture the elevations of the church.  However due to the building design and the lay of the land, the roof was almost completely obscured and to overcome this, a drone was operated from the ground using separate flights for each side of the church, in order to keep the drone in sight. To match the dataset from the drone to the dataset from the terrestrial laser scanner, it was essential to get good coverage of the site and in order to register the aerial drone data, numerous common points between the terrestrial and aerial drone data were picked. The drone data was then converted to a pointcloud and combined with the scan data to get the comprehensive data set required to create the drawings for the client.


Detailed roof plan and 2D elevations of the church

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


2D elevations of the church

 

Photogrammetry is also often used for detailed historic recording to create ortho-images and textured meshes, where the quality and the true colours can provide conservation specialists with extra information that is hard to achieve from other techniques, such as laser scanning alone.


Aerial photography taken at Rochester Cathedral

Above: An example of Aerial photography taken at Rochester Cathedral using Aerial drones.


To summarise, Photogrammetry is very much a developing method of surveying and capturing information thanks to massive advances in both the hardware and software involved. It is also fuelled by the rise in popularity and availability of drones, both for commercial and private use. Whilst working with the latest technology, at SUMO we are keenly waiting to see and embrace the next generation of photogrammetric solutions that are no doubt waiting in the wings for this very modern surveying technique.

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