Ordnance Survey partner with OxTS to create a scalable and reliable mobile mapping and pointcloud data collection system.
National mapping agency for Great Britain, Ordnance Survey, were in need of a quicker and more cost effective way to collect georeferenced pointcloud data. Their existing method wasn’t sustainable in the long-term so they turned to Datron Technology and OxTS to help them develop a convenient, low-cost mobile mapping system that could be used ‘off the shelf’.
Ordnance Survey wanted to build a mobile mapping system that would allow them to create accurate, georeferenced pointcloud data that they could use for feature identification and extraction. The system needed to be cost-effective and have the ability to scale nationally.
Who is Ordnance Survey?
Ordnance Survey create, maintain and distribute detailed location information for Great Britain. They record and maintain 500 million geospatial features in the National Geographic Database of the nation making over 20,000 updates every day.
They have been mapping the nation since 1791 and have continued to evolve to meet the needs of the nation.
Innovation is at the heart of everything Ordnance Survey does and their experts are at the cutting edge of collecting, maintaining and distributing geospatial data.
Company: Ordnance Survey
Country: Great Britain
Solutions: xNAV650 Inertial Navigation System
OxTS Technology Features: OxTS Georeferencer and Boresight Calibration Tool, gxRTK RTK/PPK tight-coupling
Partner: Datron Technology
LiDAR: Velodyne VLP-16
Ordnance Survey is an experienced user of mobile mapping technology. They have in the past used expensive high-grade technology to create accurate, georeferenced pointcloud maps.
Whilst this method works, using high-grade, expensive systems for a long-term data collection programme isn’t manageable or sustainable. They required a lower cost setup that was simple to use, and could easily scale.
The new system needed to enable the Ordnance Survey team to reliably create accurate georeferenced pointclouds that could be used for feature identification and classification.
The first challenge Ordnance Survey faced was to build a system that would give them the ability to create an accurate digital representation of the surrounding environment – a 3D pointcloud. The features within that pointcloud would be subsequently labelled and segmented where necessary.
To create the pointcloud Ordnance Survey would have to build a mobile mapping system that could be mounted on a vehicle. It would need to include a number of components such as a LiDAR sensor, cameras and an INS.
Whilst they already had the LiDAR sensor, they required an accurate INS to provide the position, navigation and timing information needed to create the pointcloud.
Another challenge Ordnance Survey needed to overcome was software integration.
Previously they used the Autoware/ROS technology stack alongside a Velodyne VLP-16 LiDAR sensor to allow them to simultaneously collect LiDAR and GPS-RTK data. However, they quickly realised that without investing significant amounts of time into software development, they wouldn’t be able to time-synchronise and merge the two sets of data. This meant that they had to rely on existing ground control points to georeference the pointcloud data – a method that is susceptible to GPS/RTK dropouts and therefore isn’t suitable for building a long-term mobile mapping strategy.
To overcome these challenges, Ordnance Survey needed a cost-effective mobile mapping system that allowed them to concurrently collect accurate location, navigation and LiDAR data. The chosen solution also needed to provide them with a way to quickly and simply combine the two sets of data to create time-synchronised, accurate 3D pointclouds.
The mobile mapping system that Ordnance Survey developed included the following hardware components:
- 1 x Velodyne VLP-16 LiDAR sensor
- 8 x cameras with 360-degree coverage (with redundancy for future sensor fusion)
- 1 x OxTS xNAV650 Inertial Navigation System
They mounted the system on a Streetdrone Twizy which is a self-driving capable vehicle.
Ordnance Survey was already aware of OxTS through the Autoware and Streetdrone communities. However, it was only when the business requirement appeared that they looked closer at OxTS to understand what could be achieved. They also engaged with local, UK-based channel partner, Datron Technology, to learn more about the OxTS hardware and software portfolio.
Datron has been an OxTS partner for many years, and helps OxTS customers make technical and commercial decisions prior to purchase. They also handle first-line post-sales support.
Through their own research, and by working closely with Datron, Ordnance Survey decided that a combination of the OxTS xNAV650 INS, working in conjunction with OxTS’ LiDAR georeferencing software, OxTS Georeferencer, would help them achieve their goals.
There were a number of reasons for this decision:
Firstly, through the tight-coupling of cutting edge MEMS IMU sensors and survey-grade GNSS receivers, the xNAV650 gave Ordnance Survey the ability to capture highly accurate position, navigation (heading, pitch and roll) and timing measurements that they used to create precise 3D pointclouds. The hardware is also cost-effective and it’s small size and low weight made it simple to mount.
OxTS Georeferencer also had an important role to play in the decision. The software has built-in software integrations with many LiDAR sensors including the Velodyne VLP-16 which Ordnance Survey already use.
A high-grade miniature INS from OxTS. It uses survey-grade dual frequency GNSS receivers and custom MEMS IMU for centimetre-level position accuracy, precise orientation and true heading. It logs the navigation data on internal storage for downloading and viewing post-mission. For many applications, such as corridor mapping and precision agriculture, the xNAV650 provides one of the best price/ performance ratios on the market.
OxTS Georeferencer is OXTS’ proprietary LiDAR data georeferencing software. It takes the position and navigation measurements from an INS and combines them with the raw data from a wide range of LiDAR sensors through a simple ‘drag and drop’ method. An additional boresight calibration tool allows OxTS Georeferencer users to take advantage of a simple LiDAR and INS sensor calibration method to eliminate blurring and double-vision from pointclouds.
The pre-built integrations with the Velodyne VLP-16 meant that Ordnance Survey didn’t have to spend any time writing code to georeference the Velodyne VLP-16 data – this work has already been done by OxTS.
They simply had to collect the LiDAR data alongside the navigation data from the xNAV650 and using the simple ‘drag and drop‘ method within OxTS Georeferencer Ordnance Survey was able to georeference the LiDAR data in a matter of seconds.
Another feature available within OxTS Georeferencer, the boresight calibration tool, has been used effectively by the company.
The coordinate frames of the LiDAR sensor and INS must be calibrated precisely otherwise the resulting pointcloud can be susceptible to blurring and double-vision. This is something that can be very difficult to achieve by eye.
Having access to the boresight calibration tool meant that Ordnance Survey simply need to survey two static ‘targets’ from various angles and distances, and at the click of a button OxTS Georeferencer is then able to calculate the angles to a tenth of a degree.
As Ordnance Survey’s set-up is quite static the boresight calibration only had to be conducted every so often. Further to purchase, Ordnance Survey are supported by Datron who helped them choose the right configuration and aided integration with their existing LiDAR sensor.
Although still early in the data collection and processing phase, the results gained up to now have been very promising. So far Ordnance Survey has been able to collect and process data from a local town, and compare it to both a ground-truthed aerial pointcloud, and a LiDAR pointcloud collected with a high-end mobile mapping system.
Despite the vast difference in price between the two systems the results have been equally impressive.
Arguably however, the most pleasing aspect of the project so far is how the xNAV650 device and OxTS Georeferencer have impacted Ordnance Survey’s workflow and improved efficiency.
The xNAV650 includes as standard, NAVsuite, a software toolbox that allows users of OxTS INS devices to configure, monitor, analyse and post-process their INS data. Ordnance Survey found both NAVsuite and OxTS Georeferencer to be simple and straightforward to use allowing them to get up and running quickly.
“The biggest change has been the convenience of the off-the-shelf nature of the collection, and the processing. This has saved many development hours. The software has also been very intuitive to use”
James Clarke, Research Software Engineer – Ordnance Survey
Although Ordnance Survey is still early in the adoption phase they have been very pleased with both the clarity of the pointcloud and also the impact on cost and efficiency.
By using a combination of the OxTS xNAV650 INS and OxTS Georeferencer alongside their Velodyne VLP-16 LiDAR sensor and Streetdrone Twizy vehicle, they have reduced their mobile mapping costs and improved efficiency while at the same time maintaining the quality of their final product.