Recent developments in using single-frequency dual-satellite navigation system for RTK application (L1 GPS + L1 GLONASS, or L1 GPS + B1 Beidou), with more satellites overhead at any given time resulting in much higher availability getting ambiguity fixed solution, it has brought lower-cost single-frequency centimeter-level accuracy RTK receiver closer to reality. Using GNSS Radar, below figures show what satellite availability might be like over a 12 hour satellite orbit period at different locations.
In East Asia, Australia, and India, there are more GPS + Beidou satellites over the horizon than GPS + GLONASS satellites. In Europe and South Africa, slightly more GPS + GLONASS satellites than GPS + Beidou satellites. In North America and South America, number of visible Beidou satellites is low.
With goal of developing a small low-power single-frequency RTK receiver module, for ease of debugging, initial development of RTK software is done on a PC, with below recent results:
Although above image looks wobble a bit, the result on the athletic track should be good, considering it’s not easy to hold the antenna pole straight and perpendicular to the ground without shifting the antenna slightly.
For comparison, below is from jogging around campus, logged using Nike+ using Galaxy Note 3; four passes over a same route, with fifth path making the smaller round.
With more available satellites using two satellite constellations, time to resolve integer ambiguity achieving fixed RTK solution is much shorter than using single GPS constellation alone (90 sec with 7Km baseline in above example), and it has high availability at any time of day. Above test results show exciting promising potential for emerging applications requiring high position accuracy using lower cost single frequency RTK receiver.
A complete SMD receiver module prototype about the size of 25mm x 25mm will be developed, beginning schematic design next week. A separate interface adapter board will have accommodation for wider power input range, data logging, and other interface if needed. Now at beginning development stage of the target hardware, if there are developers interested in adding software support making this RTK solution workable with Pixhawk or Ardupilot, would be happy to try accommodating the needed hardware interface on the board design. Cheers!