How to use synchronised video to better understand external conditions in GNSS testing
A major issue encountered in testing GNSS products such as navigation devices lies in understanding the effect of external conditions on your device. Why exactly was there a drop-out or multi-path reflection at a particular point in the test, and what caused it?
Developing and improving GNSS devices is more complicated when the causes of effects are not fully understood. However, if you were to understand exactly why an error took place, then development can progress much faster.
Video VBOX & LabSat for Synchronised Video
Recording video at the same time can be used as a solution to this issue, because it enables engineers to see the environment in which the test is taking place, helping to understand the causes of some of the results. However, it's easy for video to be out of sync with the device under test in playback, which creates confusion.
A unique feature of the LabSat GNSS recorder, replayer, and simulator, is the ability to record video at the same time as the GNSS RF data. This is achieved using the powerful Racelogic Video VBOX, which includes up to four bullet cameras, the ability to log data from a number of sources, and overlay it graphically on the video, instantaneously.
What does this mean for GNSS Device Testing?
If you're a developer, this means you can film your test route alongside the GPS and GLONASS RF data and play it back in sync, with a graphic overlay. This gives a unique insight into the source of the recorded signal and is ideal for developing GNSS based systems. It also enables you to demonstrate equipment at exhibitions and in training.
LabSat replays a test drive through a SatNav alongside synchronised Video VBOX video, providing developers with information about real world conditions encountered during recording.
How do you set up the video & data synchronisation?
The Video VBOX is simply placed in the test vehicle at the same time as LabSat, and the internal GPS engine time stamps the video so that the RF data can be synchronised with the video when replayed on the bench. Not only is the video perfectly synchronised, but GNSS data (and other data sources) can be graphically superimposed on the image during recording.
This is made possible because LabSat contains an internal GPS engine which is connected to its RF output channel. Therefore, during a replay, this GPS engine tracks satellites contained in the original recording, and the time-stamp from this GPS engine is sent over a separate serial connection to a PC which automatically synchronises with the UTC time embedded in the Video data.
You can pause, jump forwards, or backwards on the video, and then when you press play again, the video automatically jumps to the new synchronised position.
A powerful test environment
As Video VBOX is also a GPS data logger with CAN, you can record many other signals at the same time, and overlay these on the video, producing a very powerful test environment. All overlaid graphics are user-customisable with Racelogic's included software.
To see the video, in perfect time with the GPS/GLONASS RF playback, provides engineers with valuable information about the real world conditions encountered during recording.