Discussion about implementing RTK GPS in ArduPilot
Video by Dennis Baldwin showing how to set up the EMLID Reach
Does ardupilot 3…0 support cm level GPS coordinate resolution required to use RTK data ? There is some confusino about FLOAT versus DOUBLE INTEGER. Wiki claims that cm level (10^-7) resolution was added in APM 2.43. Does anybody know for sure ?
The simple answer there is yes and no 
To be precise, the displayed accuracy on the GCS is to 6 decimal places (but 7 on the data flash logs) which can only give a 1.7cm indicated variance at best.
As we are now working with RTK at a +/- 6mm accuracy this 6 decimal place display is not enough.
We will need at least 8 or 9 decimal places to ensure we are getting the accuracy.