Horizon Imaging

2700 square metres of Royal Hampshire County Hospital roof inspected with drone in Winchester

Last month we were commissioned to inspect over 2,700 square metres of roof structures at the Royal Hampshire County Hospital in Winchester. This was one of our largest aerial inspection projects to date and involved a significant amount of planning as the hospital had to remain open whilst the work was being carried out. To complicate matters further, the hospital is directly opposite Winchester Prison — a very sensitive site with an understandable concern for drones flying anywhere near their land. 
Thanks to our meticulous planning, the shoot was a complete success, with the entire roof structure being inspected from the air in under 3 hours. This saved our client, surveying firm AECOM considerable time and expense when compared to the only feasible alternative — cladding the entire building in scaffolding! 
The first task was to find out when the site was at its quietest – to minimise the number of people that would be wandering around / into / out of the site. According to the estates team this would be a weekend morning – as early as possible! Given the time of year, we couldn’t go too early or the sun wouldn’t have risen! Bearing this in mind, it was decided to start the work around 0830 in the morning. 
The next task was to visit the site prior to the shoot itself and establish the various points where members of the public could enter / leave the site – this information was needed to help us create a thorough risk mitigation strategy. After photographing all the pedestrian entry / exit points around the site, we put together a plan for cordoning off the majority of the access points, leaving only a few which could be marshalled on the morning of the shoot itself. This plan can be seen below. 
Part of the risk-mitigation plan for the drone aerial inspection work at the Royal Hampshire County Hospital, Winchester. Click to enlarge. 
Next we had to get permission to fly the drone within a few hundred metres of Winchester Prison which was on the other side of the road to the hospital. This was achieved by speaking with the prison’s Head of Security who granted permission for the work to proceed on the basis that the drone remained over the hospital’s land at all times and that we provide him with the date and time when the work would be taking place. 
The final step was to submit a ‘geofence unlocking request’ to DJI, the manufacturer of the drone we would be using. As part of DJI’s ongoing efforts to improve the safety of their drones, and the safety of sensitive locations such as airports, football stadiums and prisons (amongst others), these sites are ‘locked’ by default, meaning that if a drone tries to take off within a certain radius of one of these sites, the motors simply wouldn’t start. Similarly, if a drone was flown towards one of these sites from outside the locked zone, it would stop ‘in its tracks’ as soon as it hit the boundary of the locked zone, and enter a static hover. 
However, there are times when it is perfectly safe to fly within one of these locked zones – and this work at the hospital is a perfect example. DJI allow their locked zones to be unlocked provided sufficient information is provided which proves the drone can be operated safely. The required information includes: 
  • Copies of the drone operator’s commercial licence and Public Liability Insurance 
  • A letter / email from the owner of the sensitive site (in this case the prison) granting permission for the work to take place 
  • The serial number of the drone and radio-control handset being used (this allows DJI to send a specific unlock command to the drone that will be used for the work) 
Within 7 days the unlocking request was granted and the shoot could then proceed. 
After waiting for the next calm Saturday morning (and it took quite a while until we got one of those back in February!) the work was undertaken. 
Our DJI Inspire 2 in-flight taking 20-megapixel still photographs of the roof of the hospital building. Click to enlarge. 

The cordons and road closures around the site had been put in place the previous night as per our risk mitigation plan, meaning the front car park was virtually deserted when we arrived – just what we needed. 3 members of Estates staff from the hospital, the surveyor from AECOM and our pilot then worked closely together for just over 3 hours, slowly working their way around the perimeter of the buildings of interest a) taking high-resolution aerial still photos of every nook and cranny of the roof structure, and b) ensuring that no members of the public strayed into the flying area – either from inside or outside the building. All 5 team members were in close radio contact the whole time, which meant that members of the public who needed to enter or leave the hospital could still do so – but only when it was safe to do so. 

A selection of the roof inspection photographs taken by our drone. Click to enlarge. 
Photos were taken at the front of the building first as this was the area where footfall would increase most rapidly as the morning progressed (the main entrance of the hospital is at the front of the building). Once the front area had been surveyed the car park was re-opened and the rear sections of the buildings were surveyed. 
The inspection work was a complete success, and our client recently provided us with the following kind feedback on the services we provided: 

Horizon Imaging undertook an aerial photographic survey of the upper floors and roof of the main Butterfield Building of Winchester Hospital, as part of our structural survey of the building. The high-resolution photographs of these areas enabled us to view parts of the building not easily visible without scaffolding, thus introducing a large cost and time saving, as well as removing a number of health and safety hazards. Overall it was an incredibly efficient process to capture a large amount of data. 

Do you manage a building which has an ageing roof that is starting to require attention? Perhaps you’re in the process of investing in a commercial building and want to know that your investment is in good condition? Or perhaps you are a structural surveyor and you need to know the condition of the roof of a building so you can complete your building condition report? We can help with all the above – drop us a line today for an informal chat about using drones for conducting your roof inspection work.