Being able to detect and report the weather is important for a tower controller, so they can understand the effects it will have on the operation and procedures. This skill is even more valuable when controlling from a digital tower, where you are not actually where the weather is.

For the London City digital tower project we needed to see and document a variety of weather events at the airport, and the weather did not always play ball, clear sunny days were not what we needed. We needed snow, hail, fog, rain, the lot.

Over many months, using recordings from the camera systems and data from the weather logs, we compiled case studies of all the met events the CAA and Met Office required. We then spent many hours studying these to assess the performance of the system and collate training material.

Overnight patchy fog. Notes how the fog patches take on a greenish hue due to the ambient lighting at the airport

The met observations had to be done day and night, so we could show that observing the weather using cameras was the same, or better, than would have been seen if at the airport. As well as the case studies, we also conducted simultaneous observations, having Met Office airport MET auditors at the conventional tower and at the digital tower in real time.

We spent many evenings with the Met Authority and Met Office in the digital tower reviewing the case studies and observing the weather on the screens. This work was part of my wider system optimisation tasks, to make sure the image on the screens allowed us to do the met assurance observations and provide the ATC service, so we spent a lot of time fine-tuning the image, and after a lot of work, we gained approval for providing met and the ATC service using the digital tower.

Cumulonimbus and a ‘shower in the vicinity’ is clearly detectable to the east (the grey boxes on the screens show this is a replay of a recording, not live view)

The digital tower brings advantages to observing weather; the compressed panoramic view — with a 360 degree view compressed into 225 degrees makes it easy to see all the cloud cover at the airport, which you wouldn’t see without turning your head in a conventional tower. We can use the pan tilt zoom cameras to zoom into puddles to view rain, just as we would with binoculars in the towers, but it is slicker with a click! We also introduced a “Met” scan on the pan tilt zoom cameras which allows you to see clouds you would not normally see at night.

Darren Hardy, Met Office aviation observations advisor

The provision of accurate and reliable weather observations at airports is important for the safety and planning activities of aircraft. The CAA has established requirements for airport observations in the UK, based on international regulations.

The Met Office provides aviation forecasts on behalf of the CAA for aviation. The forecasts include Terminal Air Forecasts (TAF) which cover the operating hours of London City Airport. The accuracy of the TAFs issued by the Met Office are dependent on the quality and reliability of weather observations made at airports, known as METARs (METeorological Aerodrome Reports). In fact, TAFs can only be provided if the Met Office receive continuous METARs based on accurate observations.

We were particularly interested to understand if, and how, making weather observations might be influenced by using digital imagery.

Tall buildings are a good reference for estimating cloud base low cloud. Here the tops of the buildings at Canary Wharf are around 600ft. Reported cloud base is 400ft

The culmination of this work has helped NATS to achieve assurance that the qualified personnel making airport weather observations can continue to provide high quality observations even when physically remote from an airport. In turn, this has provided the Met Office with assurance that we can continue to maintain our London City airport TAFs to the standards expected by our stakeholders.

You can find out more about the London City digital tower transition.


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