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Development and launch of centimeter accurate enhanced GPS with realtime correction

The Japanese government is eyeing 2020 to begin promoting exports of a GPS technology accurate to a several centimeters. This should help services that need pinpoint accuracy clamoring for the system.

An H-IIA rocket carrying the Michibiki No. 3 quasi-zenith satellite blasted off from the Tanegashima Space Center in Kagoshima Prefecture, southwestern Japan.

Japan’s improved GPS is expected to prompt the development of a range of services in sectors from autonomous driving to cargo management.

The planned launch of Michibiki No. 4 in October, if successful, will complete a four-satellite constellation. That is enough for one of the satellites to be above much of Asia, including Japan, at all times. Services in the region that adopt the system will be able to rely on the constellation 24 hours a day.

New positioning service promises pinpoint accuracy in Asia.

Tokyo also plans to engage the Association of Southeast Asian Nations in talks to seek ways for its members to use the new system.

Japan’s Quazi-Zenith Satellite System (QZSS) is designed to augment Japan’s use of the U.S.-operated Global Positioning System (GPS) satellite service. By precisely correcting GPS signal errors, QZSS can provide more accurate and reliable positioning, navigation, and timing services.

The four satellites will follow an orbit that, from the perspective of a person in Japan, traces an asymmetrical figure eight in the sky. While the orbit extends as far south as Australia at its widest arc, it is designed to narrow its path over Japan so that at least one satellite is always in view high in the sky—hence the name quasi-zenith. This will enable users in even the shadowed urban canyons of Tokyo to receive the system’s error-correcting signals.

To correct the errors, a master control center compares the satellite’s signals received by the reference stations with the distance between the stations and the satellite’s predicted location. These corrected components are compressed from an overall 2-megabit-per-second data rate to 2 kilobits per second and transmitted to the satellite, which then broadcasts them to users’ receivers.

In QZS-1 trial tests, Yasumitsu notes that the average accuracy is about 1.3 centimeters horizontally and 2.9 cm vertically.

There are other competing centimeter accurate positioning systems.

Real time kinematics

High precision positioning can be achieved by combining Global Navigation Satellite Systems (GNSS), such as GPS, GLONASS, Galileo and BeiDou, with Real Time Kinematics (RTK) technology. RTK is a technique that uses the receiver’s measurements from the phase of the signal’s carrier wave. These measurements combined with corrections from a local “base” station or virtual base station, allow the receiver to solve carrier ambiguities and provide cm‑level accurate position information to the end‑user, a moving device, typically is referred to as the “rover”.

The demand for lower priced high precision technology is growing rapidly, as evident in the areas of precision agriculture, UAVs, and robotic lawnmowers. However, due to size, power, and cost restrictions, existing high precision solutions have been unable to meet the demands of these markets. u‑blox has developed the recently launched NEO‑M8P to meet these growing demands. Together with u‑blox’s GNSS expertise and the implementation of RTK technology, the NEO‑M8P provides centimeter‑level precision for the mass market

Swiftnav Duro™ is a ruggedized version of the Piksi® Multi RTK GNSS receiver. Built to be tough, Duro is ideal for agricultural, robotics, maritime and outdoor industrial applications. Duro is designed for integration into your existing equipment. This easy-to-deploy GNSS sensor is protected against weather, moisture, vibration and the unexpected that can occur in outdoor long-term deployments.

Centimeter-Level Accuracy for autonomous devices. Self driving vehicles require precise navigation—especially those that perform critical functions. Swift Navigation’s Piksi Multi module within Duro utilizes real-time kinematics (RTK) technology, providing location solutions that are 100 times more accurate than traditional GPS.

The Swift Navigation’s Starling™ software navigation engine, running on top of Swift Navigation’s Piksi™ Multi Real Time Kinematics (RTK) GNSS Receiver hardware, receiving network corrections via cellular Internet. This system was tested in open-sky conditions on an 8-mile route in San Francisco, California. The circular error probability (CEP) was as follows—the CEP50 positional accuracy for the run was 1 cm and the CEP99 was 35 cm.

The Swift Navigation system improves robustness by providing excellent 99th percentile accuracy, not just 50th percentile accuracy, as is often quoted. The system also moves gracefully from the centimeter-accurate fixed RTK mode to the decimeter accurate float RTK mode, still providing substantially improved positioning performance in degraded signal conditions.

Centimeter-Scale GPS for Europe

The U.S.-operated Global Positioning System (GPS) is accurate only to about 10 meters, while Europe’s corresponding Galileo system, with 18 of its 24 satellites currently in orbit, has an accuracy of 1 meter. Yet even 1-meter accuracy is not sufficiently precise when it comes to ensuring that autonomous vehicles, for example, maintain safe lane positioning and avoid certain obstacles.

Germany’s Bosch and Geo++, U-blox of Switzerland, and Japan’s Mitsubishi Electric announced the establishment of Sapcorda Services last Tuesday, a joint venture to provide global navigation satellite system (GNSS) positioning services of centimeter-level accuracy via satellite transmission, mobile cellular technology, and the Internet.

Sapcorda plans to augment GPS and Galileo positioning data in Europe by employing surveyed reference stations on the ground. These stations will monitor satellite signal errors, especially errors caused by the ionosphere and the troposphere, which can bend a satellite’s signal. The stations will send the data via the Internet to a master control center that corrects the errors and transmits the results back to the satellite and also to mobile cell towers for broadcasting to user terminals.

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