By Bogdan Bujoreanu, Building Surveyor, Kaizon
One of the goals at Kaizon is to deliver innovative solutions to provide successful outcomes for our clients. After looking into the benefits it could provide our team, Kaizon purchased a fit-for-purpose drone to support our building and facade surveys and technical assessments.
Some of the work at Kaizon involves analysing and assessing external details of high-level buildings. These details can often be hard to see from the ground, or even from the roof (and often we need to assess the roof but are unable to safely get on it). That is where a drone becomes useful – the team at Kaizon use the company drone to obtain photographs and videos of areas where details are needed, but which are not easily accessible to a surveyor.
The use of the drone to survey roofs or facades on multi-storey buildings has mitigated danger by reducing the use of ladders, cherry pickers, scaffolding, and walking on slippery surfaces.
Kaizon has been hired to carry out a condition assessment on a multi-story building in Auckland CBD. The project involves assessing the condition of the facade and the roof. This is where the drone became extremely useful to us. The team used the drone to take photos and videos of the external envelope of the building. This meant the job was able to be carried out a lot quicker and without the need for other tools such as, cherry picker or someone rappelling down the building to take photos, both of which increase the risk on the surveyor, are more expensive and also require extensive training. The drone was very beneficial both to us and the client for this project. It allowed us to capture all the required data in a safe environment and in a very timely manner.
Things to consider when flying a drone
Flying a drone, however, is more complex than what people realise and is not as easy as it may appear. There are many factors that our surveyors need to be aware of. One of the most important rules of flying a drone is that if you can’t see it – then it’s not safe to fly it. The drone must always be kept in your line of sight, this ensures that if you encounter an obstacle you will be able to safely avoid it without causing harm to either property or people. Furthermore, keeping an eye on your drone could save damaging the drone and avoid financial loss.
Weather conditions are also a big factor when deciding if the drone can be flown or not. Drones are light which means gusts of wind can move them easily and sometimes it is hard to predict where the wind is coming from. It is not recommended to fly the drone when the wind is over 9.7. When the weather is concerning the pilot needs to use his or her judgment and make an assessment based on their skills if the drone can be flown.
Being aware of the area you are flying in is another important aspect of flying. In New Zealand there are many areas where drones are not allowed without prior permission, this may be due to proximity to airports/aerodromes, military operating area or just temporary restricted areas. Calling the controlling authority ensures that they are aware of you operating in the area, and in case something goes wrong (i.e you lose control of the drone) they will be quick to react and either ground all aircraft or divert flights away from the area.
Losing control of your drone doesn’t happen very often, but it is still a risk, especially when flying in populated areas where there is radio interference. The drone is technically a radio transmitter and receiver that works on different frequencies, however, in built-up areas there are many devices such as mobile phones, antennas, etc, that use radio frequencies and that may interfere with the communication between the drone and the remote. This can have serious consequences such as causing the drone to become inoperable resulting in the drone drifting away until it either runs out of battery, crashes into an obstacle or – in some lucky cases when the connection between the remote is established, control is regained.
When using a drone as a residential surveying tool and flying above people’s houses, the drone operator must make sure that the owner of the house or the land you are flying over has given their permission.
Wind Tunnel Effect, Downdraught Effect, and Channelling
Flying in populated areas with multi-story buildings around can create a phenomenon called the ‘wind tunnel effect’. This means the wind is accelerated and is stronger than you anticipate. Accelerated winds near skyscrapers are caused by the “downdraught effect”, says Nada Piradeepan, an expert on wind properties at engineering consultancy firm Wintech. This happens when the air hits a building and with nowhere else to go, is pushed up, down and around the sides. This results in the air being forced downwards which increases wind speed at street level. If several towers stand near each other there is an effect known as “channelling”, a wind acceleration created by air having to be squeezed through a narrow space. It is recommended not to fly a drone nearby multiple buildings, and always keep a safe distance so that if you’re hit with gusts of wind the pilot has time and space to regain control.
Watch out for Birds
An unexpected challenge we faced while flying our drone, especially in coastal areas, is the presence of birds. Birds can feel threatened by the drone and start attacking it. This is not only risky for the drone but the birds as well, as the drone propellers can cause serious harm to the birds. In these situations, the pilot has to use their common sense and determine whether it is safe to fly the drone in those conditions. From experience, waiting a few minutes seems to help as birds lose interest. That is why having a second person while flying the drone can be extremely helpful, the second person not only looks for birds but keeps an eye out for obstacles that the pilot might have missed.
The importance of a spotter
Another advantage of having an extra person is that they can keep curious people away from the pilot and answer any questions that pedestrians might have about the operation. This way the pilot’s attention is fully on the drone and on operating it safely. Having a competent spotter is mandatory when flying close by uncontrolled aerodromes as they can keep an eye for low flying planes. As your drone is allowed to go up to 400ft (120m) the chances of meeting a low flying plane are quite high.
Learnings from the Training Course
To ensure that our drone operations are carried out safely and legally, Kaizon arranged for me to attend a training and test session with one of the best assessors in New Zealand.
Throughout the two-day training course, legal and technical matters were covered, including learning how to use your drone in emergencies. What some people may not know is that drones generally use GPS as their main navigation system and connect to the satellites that are orbiting the earth to find and maintain an accurate position. However, when radio interference occurs the GPS signal can be lost so the drone won’t be able to hold position. That is when the drone enters what is called ATTI mode or altitude mode. This means that the drone will be able to hold a vertical pattern, but on a horizontal plane, it will be harder to control. This is where the training session was essential. Learning how to control your drone when the GPS signal is lost is a very important skill to have. The drone will not hover independently and the smallest gust of wind will throw it off trajectory. If the pilot doesn’t know how to cope or react to this, the consequences can be terrible. Most drones such as DJI Phantoms or DJI Inspire can manually change from GPS to ATTI mode, and that means you can train to react to how the drone moves with or without GPS. With the smaller drones (such as DJI Mavic) the ATTI mode is automatic so it only comes on when there is either radio interference or not enough satellites available to obtain an accurate GPS positioning. This can prove to be dangerous because it can happen at any moment and if the pilot is not aware of this the drone can easily drift away and crash.
Another interesting aspect learnt during this course what reading and understanding Airmaps (the same kind that airline pilots use) and knowing where to look for more information regarding the airport and airfields.
There are websites such as Airshare that simplify those maps and make it easier to read, however, these might not contain recent NOTAMs (Notice to Airmen). Notice to Airmen is a notice filed with an aviation authority to alert aircraft pilots of potential hazards along a flight route or at a location that could affect the safety of the flight. What this means for drone pilots is that some airspace might be restricted for a few hours or a few days due to certain events happening. One example is when the US Vice President, Joe Biden, visited New Zealand in July 2016. A NOTAM was issued for Auckland CBD where flying was not permitted from ground level to 5000ft. Being aware of these notifications could save you from any complications from flying in restricted airspace.
Flying the drone has many advantages such as reducing the risk to surveyors, getting accurate details from tricky spots, and providing accurate and quick reports to clients. There are many aspects of drone flying that pilots need to be aware of, including the safety and integrity of the drone, the surroundings and any other people involved. Take all the practical steps to reduce and mitigate any risks. Ensure that the drone is in working order before you fly, that can be easily done by creating a pre-flight checklist and following it when you are on site. And lastly, have some fun while you’re doing it.
Written by Bogdan Bujoreanu