First of all I would like to say that I am new to gis-se and as such I will try to comply as much as I can to your policy. That said I am actually doing a little project which as the title says relates to RTK-GPS. I am trying to make use of RTKLib which would be familiar to the people reading this.
Following the paper written by the creators of RTKLib I am replicating their low cost RTK receiver with of course more up-to-date parts such as U-blox LEA-6T instead of the U-blox LEA-4T. However, as I am in the UK I do not have access to a free RTK base station within 20 Km range. I therefore looked for a way of making a base station which from a logical deduction could be a second receiver (fix) acting as a base station (for double differenciating) and connected to the Rover (first moving receiver). Anyway, after a brief research I found this setup that seems to be good enough.
My questions so far are the following:
- Would that setup work with my receiver?
- Is it good enough? Can I still achieve cm-level precision?
If you any other source of information or examples that would help get a better grasp of RTK-GPS I would be very appreciative.
During my research, I read about the whole theory and did understand it to an acceptable level. However, I still have one thing that I cannot understand. For RTK, we perform an ambiguity resolution which consists in finding the integer cycles of the wavelenght. There are many techniques (even some working with floats) but why an integer number gives a better precision? Is it because of the PLL's? Because the wavelength for L1 for example is about 19 cm so I guess an integer number would give a precision within 19 cm, is that correct?
Best Answer
To go back to the basics of GPS positioning, you need to know the distance between the receiver antenna and each of the satellites the receiver is tracking. You need a minimum of 4 satellites to determine your position.
The distance antenna-satellite is equal to a number of full wavelengths plus a partial wavelength.
The receiver can only measure the last wave, or actually the partial wavelength.
The ambiguity is the number of full wavelengths separating the antenna from the satellite. So resolving the ambiguity is determining the number of full wavelengths.