Self-driving cars on town streets and highways - a sight that might be a scene from a futuristic movie or comic book - is gradually becoming a reality. In 2010, the quasi-zenith satellite "Michibiki" was launched. The system is Japan's space-borne positioning system (that calculates location information), sometimes referred to as the Japanese GPS. Since the Michibiki started operating directly above Japan, professionals in various fields have been doing research to demonstrate applications of the quasi-zenith satellite system.
Aisan Technology, Co., Ltd. headquartered in Nagoya, Aichi Prefecture, is one such organization. We interviewed the company to learn about the use cases of quasi-zenith satellites, a road lane recognition navigation application the company has demonstrated, and their research and development of maps that are used with the navigation application programs.
Aisan Technology is an established surveying operations software developer and has been at the forefront of satellite positioning R&D activities. Commissioned by the Satellite Positioning Research and Application Center (SPAC), the company has been assisting in demonstrating use cases for "Michibiki" from early on. At one point, Aisan Technology noticed that there had been few field trials to demonstrate the Michibiki's sub-meter level (2-3 m accuracy) positioning enhancement capability for moving objects, such as cars and trucks. In 2013, Aisan decided to perform a series of tests to validate the positioning accuracy [of the Michibiki.]
What Aisan did was develop a simple navigation application program that recognizes road lanes using the Michibiki's data and digitized road maps for the navigation app. A 2-3 meter positioning accuracy should be adequate for recognizing lanes.
Aisan already had expertise in location data analysis but it needed accurate maps on which the location data were rendered. Even if space-borne precise location data is available, if the map itself is not precise and accurate, the location data rendered on the map won't be correct. Both are required to tell the location accurately. Aisan, then, selected "Mobile Mapping System (MMS)" by Mitsubishi Electric Corporation, which Aisan already had, to create precise road maps. The MMS, a vehicle equipped with a GPS, laser scanners, cameras and other sensors, accurately and efficiently captures road surfaces as 3D point cloud (a collection of surface measurement data points of an object) while driving. The MMS point cloud data was analyzed to recognize the white lane-dividing lines to create the digitized map for the navigation app.
In urban environments, "multipath", that is signals bouncing off of buildings and other surrounding objects impacts accuracy of the position data. In a suburban area with open sky, there is little multipath effect and the Michibiki data and the actual lane data had good correlation. In urban areas, the satellite data projected on the map sometimes did not match with the actual lanes; in some cases the projected lanes were off the roadway.
It is believed that this issue can be resolved using the "multi-GNSS" technology combining GPS and Michibiki with other positioning satellites such as the EU's Galileo. The more satellites the vehicle can see, the more precisely the vehicle can identify its position excluding "multi-path" data.
Funded by the Cabinet Office, Aisan has been researching how to use satellite-based positioning data for a self-driving system last 3 years. A self-driving system is one of the goals of the Office's science and technology initiative called the "Strategic Innovation Promotion Program (SIP)". Aisan evolved the previous research and is validating the accuracy of multi-GNSS and other position sensing technologies for automotive use cases.
By 2018, Michibiki will be ready for commercial applications, making quasi-zenith satellites available near the zenith around the clock. This will improve the successful position data capture rate in urban and other areas with poor satellite visibility.
In addition, position data augmented with sub-meter and centimeter accuracy data will provide wider range of precision and accurate, which satisfy different requirement for use cases.
Aisan Technology says its 2013 tests successfully demonstrated the value of the Michibiki and the digitized map. It also wishes to educate the market with the technology that accurately project measured position onto the map, which is essential in using satellite-base positioning data. Aisan has expertise in ortho-rectifying technology to align the coordinates of satellite-based positioning data and the coordinates of map.
"We want to expand our technology scope for realizing self-driving vehicles, parameters and coefficients for correcting position errors on map for example. We look forward to seeing our technology being leveraged in self-driving vehicles and car navigation systems", says Aisan Technology.
The company's technology may be at the very heart of our lifestyles in the near future when self-driving vehicle and accurate navigation system is the norm.