Track Access Services using OxTS Survey+
Track Access Services (TAS) are a small UK-based company and OxTS customer that have been short-listed for several awards based on the innovative survey, design and simulation services it supplies to the rail industry. Working closely with Bentley’s rail and transit software solutions, TAS specialise not only in collecting and handling the vast amounts of data involved in large scale rail projects, but in manipulating that information in such a way that it can be leveraged at every stage of a project from concept to approval, and finally for driver training.
One of the keys to the success of TAS is their ability to integrate high-definition video filmed from a driver’s eye position (fully geo-referenced using Survey+) with other design assets such as 3D CAD models and LiDAR data. Using their own in-house software, they are able to composite the various outputs with the HD video backdrop so that CAD models and LiDAR data can be viewed in a visually-engaging real-world context.
Signal sighting application
One of the many useful applications of this is in signal sighting, as Technical Director William Bruce explains, “When Network Rail make any changes—put in new signals and so on—the changes have to be approved by a committee of interested parties such as different train and freight operators and other people in the area. Traditionally what would happen is a section of the railway line would be closed down and everyone would go out en masse, while someone held a lollipop-stick with a target on it to represent a red aspect position for example. Then everyone would stand back at different distances from the new feature and say, ‘yes, our drivers will be able to see that from Class 37 train and they’ll be able to stop in time’, and that sort of thing.
“What Bentley developed was a desktop version—so that process can now be done using a 3D CAD package where people can sit around and fully evaluate the light cones from signals and so on. But obviously there is a lot of work in making a full 3D model of the surrounding area, so there was a provision to use a video backdrop instead. The signal models can then simply be converted into the same perspective as the video and overlaid on the video imagery.”
Geo-referencing the camera
In order to do this accurately, Track Access needed to know the position, heading, roll and pitch of the camera at all times. Prior to the purchase of the Survey+, the referencing of the video backdrop was achieved with match moving—where each frame of video is analysed by an algorithm to track several key points which can then be used to calculate the relative orientation of the camera. While match moving worked relatively well in London, where the large number of buildings provided plenty of reference points, it was less effective in the countryside and in tunnels or deep embankments where there were no consistent references. A standalone GPS solution also struggled as signal blackout and multi-path meant the quality and consistency of measurements was unworkable.
“The Survey+ has proved to be the perfect solution for us,” says David Reed, Managing Director. “It’s all about accuracy. That’s the game—and people play it different ways. We explore all kinds of technologies all the time, but looking back, the purchase of the Survey+ was really a pivotal point for us.” The process Track Access has now developed is quite straight forward. The Survey+ is mounted in a train using one of our RT-Struts near to the camera. It then provides a constant stream of position and orientation measurements that can be synchronised with the video footage using GPS time.
Putting it all together
Once a survey has been conducted, the data is downloaded and post-processed using RINEX files to bring it to RTK integer accuracy levels, before being assimilated into the software that Track Access has developed. “Where we are now with the equipment, it is an integral part of what we do. We’ve got our position video system based on this technology working just fine,” says David. “We deployed this technology when re-signalling Derby train station. We built the signal sighting model, and we built a 3D model of the centre of Derby. On the extremities we made video of the route so we could do signal sighting using a combination of the detailed model in the centre and video at the extremities.”
So has the Survey+ been worthwhile for Track Access? “Initially, the biggest thing for us was the support we received from Datron Technology [OxTS’ UK representative] during our trials. That was very useful,” says David. “The whole experience of getting this equipment, taking it on, running it, operating it and the support we received with the whole package got us going. The system was a significant investment, and I didn’t know right at the beginning how we were going to afford it, but actually it enabled us to get work of substantial value which meant that we could afford to purchase it.”
You can find out more about Track Access and the innovative services they provide by visiting their website at http://trackaccessservices.com. For more information on how GNSS-aided inertial navigation systems like the Survey+ can help your company collect geo-referencing measurement, please contact us.