We provide highly accurate, but very affordable GPS positioning solutions based on PPP-RTK technologies. PPP stands for Precise Point Positioning while RTK is the “good” old acronym of Real-Time Kinematic. Whereas traditional GPS-based positioning solutions such as DGPS and RTK need correction messages created at the reference or base station, PPP-RTK does not rely on the costly GPS infrastructure.
Instead of reference stations, PPP-RTK needs SSR (state-space representation) messages. The SSR data is currently available globally at a very high cost but a couple of institutions are providing them for free. Especially, regional services are being provided in Korea and Japan based on the GNSMART server software made and maintained by a German company called Geo++. The advantage of SSR is that the required bandwidth is much smaller than those of RTK or DGPS, thus enabling transmission from geostationary satellites. On the ground, in addition, one can use a variety of communication links or broadcast medium such as LTE, 4G/5G, TCP/IP, and Digital Multimedia Broadcast (DMB).
PPP-RTK
Dilemma in GPS
From the 80s’ several GPS positioning technologies have been developed, validated, and implemented all over the world, but nobody has solved the problem of “You get high accuracy only at a high cost”. As shown in the diagram below, you get 1-3 cm or 1 inch accuracy with $10,000 GPS devices. But with cheap GPS modules, you cannot get better than 1 meter or 3 foot. Sometimes, you need submeter accuracy with a reasonably priced GPS module. Thus, we are targeting the GPS market positioned in first quadrant of the “accuracy-vs-price” diagram.
As shown in the diagram, names of our products start with RTAP which stands for Real-Time Absolute Positioning. The first character (C or L) coming after “RTAP” denotes the type of GPS signal used: C for code-pseudoranges and L for carrier phases. The last character (1 or 2) tells you how many frequencies are used. Depending on the signal type and the number of frequencies used, the positioning accuracy varies.
Implementation
There are many applications where sub-meter positioning is required, and one of the most promising and imminent fields is autonomous driving. For fully autonomous driving, most of the localization experts agree that the self-driving car needs to position itself with the accuracy of 1 meter along the driving direction and 20-30 cm across the lanes. Because the GPS positioning accuracy does not change noticeably in the horizontal plane, this requirement translates to “20-30 cm” or “1 foot”. Our product RTAP-L1 exactly fulfills this requirement.