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I currently experiment with an affordable L1 GPS RTK system based on u-blox NEO-M8T with RTKLIB and higher quality patch antenna (with ground plane). I wonder what is the role of L2 signal in an RTK system (since the expensive RTK setups seem to use L1+L2) - how much precision/accuracy will it add to the system?

  • The expensive setups not only use L2, but also better tracking techniques such as multipath mitigation, low latency for data transmission and error checking. I'm however curious about the accuracy you're achieving with this system. Would it be possible to share what you have obtained so far? – Techie_Gus Jun 6 '16 at 21:18
  • @Techie_Gus The precision/accuracy with such affordable RTK (without IMU) varies - if you have a FIXed solution it usually is mm-level, FLOAT varies from cm to dm usually. I get pretty inconsistent results (sometimes good FIX, sometimes only medicore FLOAT) thats why I am curious about L2. – Kozuch Jun 6 '16 at 22:20
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    One of the things I know is that with a dual frequency system it is possible to better model the atmospheric effects due to the fact that L1 and L2, being at different frequencies, are affected differently by the ionosphere and troposphere. – Techie_Gus Jun 6 '16 at 22:47
  • I found some explanation for L2 with RTK here - see the "L1/L2 RTK or RTK Integer" section. – Kozuch Jun 7 '16 at 9:11
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Yes, using the L2 frequency and the L2C signal can improve accuracy since it provides additional information and redundancies. The difference between the L1 and L2 frequencies provide information on irregularities in the ionosphere, while the added information in the L2C signal can help resolve ambiguities quicker and can improve reliability of the ranges to a particular satellite.

If you can get a certain level of accuracy at a certain level of speed, including the L2 information in the calculations can make it possible to derive more accurate data positions at the same speed, or similar levels of accuracy at higher collection rates.

https://en.wikipedia.org/wiki/GPS_signals#L2C

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