In trying to learn how to create a reasonably precise 3d model of my (very hilly) property, I stumbled across a product called Navspark, which appears to be a $22 arduino-compatible development board, with an RTK-capable (and RTKlib-compatible) GPS chip.
The idea with RTK is that a reference-position base-station transmits its positional error to a mobile unit, giving the mobile unit cm-level precision relative to the position of the base station. The error calculation is computationally intensive, but apparently within the capabilities of a Pi.
Is it actually possible to build an RTK-capable mobile/base pair using low-priced equipment like this? Can you link a howto or project example?