OxTS xNAV helps to meet the demands of government map-making organisations for Caledonian Air Survey.
Commissioned by the Ordnance Survey, Caledonian Air Survey needed a solution that provided not only greater accuracy than traditional aerial georeferencing methods but a way of reducing surveying costs and workflow. Learn how the xNAV250 did just that.
Caledonian Air Surveys is a small aerial survey company operating out of Inverness Airport, from where it offers a niche digital photography service covering the whole of the UK and Ireland.
Caledonian’s hardware consists of medium- and small-format digital cameras and an OxTS xNAV250 inertial navigation system, attached to a single-engine Cessna 172 light aircraft and is used in a textbook application of the technology, as Caledonian’s managing director Tim Whittome explains: “We take a lots of overlapping photographs looking straight down – what we call vertical photographs – and, together with the position data, produce a true to scale photographic map of the area.”
Clients include Scottish Natural Heritage, the Scottish Environment Protection Agency, the Forestry Commission and private forestry owners and managers. “We also do pipeline surveys,” says Whittome. “They have to be monitored every four years to see that no one has dug a hole near to them or built something too close.”
Recently, Caledonian started carrying out work for the Ordnance Survey, which uses a variety of methods to source its georeferenced aerial photography. “The Ordnance Survey works on a tiered level,” says Whittome. “For large areas, they have their own bigger aircraft and very expensive cameras, but in recent years, they’ve started using drones for areas of up to two or three square kilometres. We’re the link in the middle, between the drones and the big aircraft, and we’re still the only company in the UK doing it.”
Until a few years ago, Caledonian operated with what Whittome calls “a fairly unsophisticated” GPS set-up, which georeferenced each photo to within a few metres. “For things like forestry and so on, that was fine,” says Whittome. “But for really accurate work, we had to commission a surveyor on the ground to give us reference points. We could be taking off 50 or 100 miles from a survey site; it was quite complicated.”
The solution for greater accuracy, required by the Ordnance Survey, came in the form of the xNAV250, which allows Caledonian to create photographic surveys that are not only more accurate but also produced more quickly. “It has really transformed what we do,” says Whittome. “Without it, we wouldn’t be able to achieve the sort of accuracy that the Ordnance Survey requires.”
Other advantages include a more efficient workflow. “Quite often with the pipeline surveys the client wants a single line of photographs in a ‘north-up’ format. We rotate each image, but if the aeroplane is bouncing around, the rotations for each photo aren’t necessarily the same, plus you’re changing heading as the pipeline changes direction. Before the xNAV, we would get the Ordnance Survey maps out and measure the angles of roads on each photo, then we worked out the rotation.
“The process would take a couple of minutes for each photo, so 400-500 photos would take a couple of days. Now the xNAV gives us a file with the rotations we need for each photo, and it takes less than a morning. It’s a substantial saving in time.”
The user experience and technical support have been positive, too. “We’ve been very happy with the support,” says Whittome, who has received help and expert advice from both John Grist at Datron [OxTS’ channel partner in the UK] and OxTS on how to get the most out of their xNAV.
Contact us if you would like more information about xNAV products or details for Caledonian Air Survey.