Drones and Historic Property Management

Drones and historic property managementThe following is an article from Historic England describing how they use drone technology to manage their buildings, archaeological sites and landscapes. The original can be found on their website.

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Drones provide a useful low-level aerial platform for recording historic buildings, monuments, archaeological sites and landscapes. They can carry a wide variety of sensors including cameras, multi/hyperspectral imaging units, and even laser scanners. Drones can provide dramatic illustrative photographs of sites, but can also be used to create metrically accurate records for survey and conservation work. However, care needs to be taken to ensure drones are used in a way that is safe to both people and the historic fabric being recorded.

Although drone is the term most commonly used by the media and recognised by the public, other acronyms are these days used when referring to such low-level aerial platforms including:

  • UAV – Unmanned Aerial Vehicle (often referred to by academic researchers)
  • UAS – Unmanned Aircraft System (referred to within Civil Aviation Authority – CAA regulations)
  • SUA – Small Unmanned Aircraft, (the acronym currently preferred by CAA-UK, TSA & Historic England)
  • RPAS – Remotely Piloted Aircraft System (now promoted across Europe within the context of their civil use in the EU). This is how they are referred to in the House of Lords Select Committee report on the Civil use of remotely piloted aircraft systems (RPAS) in the EU

Colour aerial photograph showing a partly ruined stone wall and grass lawn with the craft hovering in the sky
A rotary wing RPAS in use at Kenilworth Castle © Historic England
Types of aircraft

Two types of craft are typically used for heritage-related applications:

Rotary Wing

Advantages

  • able to hover & operate in confined spaces
  • can carry heavier payloads
  • can carry a range of sensors including DSLR still & HD/4K video cameras, lidar and terrestrial laser scanners
  • gyro-stabilised mounts typically used
  • camera RAW output = better quality of imagery

Disadvantages

  • shorter battery life & slower flight speed = shorter range of operation
  • pre-planning of flight route not universally supplied or used by operators
Colour aerial photograph showing a rotary wing aircraft with a camera mounted underneath
Quad-copter rotary wing aircraft © Historic England: Photograph by P Bryan

Fixed wing

Advantages

  • longer battery life & faster flight speed = longer range of operation
  • can glide over long distances and survey larger areas in ‘strip’ form
  • pre-planning of flight route, image acquisition and overlap commonly supplied by manufacturers

Disadvantages

  • design means smaller & lighter payloads
  • typically limited to compact digital cameras
  • lack of camera RAW output, commonly restricted to JPEG = lower quality of imagery
Colour aerial photograph showing a fixed wing aircraft on the ground
Fixed wing aircraft © Historic England: Photograph by J Bedford
Regulations

UK use is typically restricted to a combined weight of less than 20kg for both drone and camera or other sensor. All aircraft, irrespective of their size, that are used within UK airspace for aerial work and for commercial gain (a valuable consideration) must comply with CAA regulations and permissions as outlined in CAP 722.

Further guidance on the survey application of drones is provided by The Survey Association (TSA) within their Client Guide on Small Unmanned Aircraft (SUA) surveys

 

Heritage use of drones

Historic England has used drone acquired imagery since 2008 and has built up long experience of using such platforms alongside other means of capturing low-level aerial imagery such as masts, kites, balloons, helicopters and planes. There is a growing use of these aircraft across the heritage sector .The imagery and data they capture can be used across multiple applications including monitoring, presentation, interpretative display, multimedia journalism, surveying, mapping and recording.

  • Monitoring of sites
    • detailed analysis of high level wall top and roof condition
    • archaeological recording of excavated features
    • capture of still and video imagery allows both real-time and off-site analysis of condition
    • typically captured by rotary platforms due to the need for high-resolution oblique imagery from specific viewpoints
Close up colour aerial photograph showing the top of the walls of a ruined tower
Close-up vertical view of the top of Etal Castle, captured by Horizon AP © Historic England
  • Presentation and interpretive display
    • On-site display using still, video and virtual images
    • Illustrations within guidebooks, journals, newsletters, research reports and websites
    • Typically captured by rotary platforms due to need for oblique imagery although some fixed wing platforms now offer an in-flight ‘tilting’ function
Colour aerial photograph of castle tower on a large artificial mound (left); image as used on guidebook
Clifford’s Tower, York as captured by UAV and subsequently used on the English Heritage guidebook to the site © Historic England
  • Surveying, mapping and recording – coupled with the growing use of Structure from Motion (SfM) drones offer the possibility to use the imagery in new ways.
    • Generation of 3D surface models for landscape and buildings
    • Overlapping still imagery (typically 80% forward & 60% side)  processed using Structure-from-Motion (SfM) software e.g. Pix4D & Agisoft Photoscan
    • Can be captured by rotary & fixed wing platforms
      • landscapes typically fixed-wing
      • buildings typically rotary-wing
    • Guidance is being prepared by Historic England
Colour screen shot showing virtual landscape with a number of blue rectangles floating in space above it
Processing imagery captured by SUA to create 3D surface model for archaeological analysis. The blue rectangles represent the camera position for each individual shot used to create the model © Historic England

The images used on this page are copyright Historic England unless specified otherwise. For further details of any photographs or other images and for copies of these, or the plans and reports related to our work please contact the Historic England Archive.

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