Updated: May 24
CASE STUDY NO 3; ST MARY MAGDALENE CHURCH, CLITHEROE, MAY 2021
CLIENT; CHURCH OF ENGLAND
TASK TYPE; BUILDING/ROOF SURVEY & INSPECTION
In May 2021, whilst engaged on another task in Clitheroe, DDV were approached by the vicar of St Mary Magdalene to see if we could carry out a building and roof survey of his 15th century church. Although the request was not driven by any obvious recent damage, he wanted a full overview of the roof and spire, to see if anything untoward had occurred over the previous winter.
Specifically, vicar Andy tasked us with providing detailed imagery of all the 3 separate roofs that covered the structure, followed by the same type of high-resolution inspection of the spire and clock tower. This imagery would then be sent over to a qualified surveyor, so it could be analysed in a nice warm office on a large screen PC, as opposed to hanging off a ladder 100ft up in the cold and wind!!
Andy had not considered using a drone in the past, and the thought only occurred to him whilst watching us filming on the nearby task. He immediately saw the huge cost and time saving, with no requirement for ladders or scaffolding, combined with the safety aspect of not having anyone working at height. We also informed Andy that he could watch us capture the imagery in real time (viewing our captured imagery), preventing us missing anything and having to come back and perform a second flight. The whole flight part of the task would be completed in under an hour, which is remarkable given the alternative of erecting any form of inspection platform around a historic building.
As with the majority of our tasks, as soon as we start to create our pre-site survey risk assessment, various concerns came to light, the main ones being as follows;
The age of the building and the cost implication if we damage it whilst in the inspection process
Maintaining our legislative distances from uninvolved people whilst in flight
Given the layout of the building, we needed to fly very closely to the clock tower and spire, so fine weather and using the right drone was paramount
Addressing each of these points in turn, we were confident of achieving all our task requirements, whilst also maintaining a safe operating environment, mainly by having the following in place;
The correct insurance whilst flying above historic buildings, combined with the right amount of public liability cover
Flying at the correct vertical and horizontal distance from uninvolved persons, and using signed cordons and marshals to prevent any unauthorised entry whilst in flight
Using a drone with reliable and robust ‘sense and avoid’ sensors to prevent any collisions when flying close to the building structures.
Before we performed the actual survey task, we carried out a thorough recce of the site and its surroundings, something we now see as an essential safety facet of a successful operation. We like to think this can set us apart from pure hobbyist flyers and can only bolster our professional reputation. Part of the recce is to select a suitable time (earlier the better) and best weather day to fly (calm and sunny, although the UK makes this quite difficult), alongside notifying any parties that may be affected by our flight.
We decided before taking off that the most efficient flight would be one that included multiple overlapping stills (48mb), each captured from the same height as we moved along the roof in 5m increments. By following this rationale, we were able to blanket photograph the 3 roofs in under 15 mins. We then moved on to the slightly trickier spire and tower inspection, again using an incremental
approach, only this time vertically as opposed to horizontally with the roofs. This allowed us to get some fantastic imagery, including the money shot of the weathervane at the top of the spire. We had the obstacle avoidance system fully engaged whilst carrying out both flights, but still had to be very accurate with our flight inputs. This is when the benefit of 10 years flying at emergency service incidents comes home to roost, flying 100% safely when under pressure.
Post task, we got the completed imagery over to Vicar Andy using a secure transfer method, and he was quick to let us know how delighted he was with the result and overall drone experience. He gave us the following quick feedback;
“I wasn’t sure what a drone could actually achieve with this type of job, but I was over the moon with the result. Both Kane and Chris were so helpful right from the off, and delivered a really professional finish whilst maintaining a totally human touch in explaining what they could and couldn’t do. I know they champion the ‘reliable, safe and secure’ service, and would finish by saying they should add ‘super friendly’. Thanks gents, you were brilliant.