Request a suggestions in Cost effective solutions in GNSS RTK for autonomous rover

Are you working with a technical team?
I suspect you’ll have to experiment to gain knowledge, and apply it to your unique situations.
I’m not here to give you absolute guarantees.
How far do your radio links work? How do the local weather and atmospheric conditions vary a different distances.
I’d say at approaching 30 km the value of the common view tends to be significantly diminished.
For post-processing the sweet-spot is around about 7 km, that’s not to say 10-20 km can’t be servicable, but you’re likely to be disappointed more often.
Perhaps look to the experiences of surveyors in your own area, and the density of stations they are using, and the use of VRS to create more localized service from more broadly dispersed stations.
You can also increase the density of your own stations, or increase the sophistication of your implementation.
https://wisconsindot.gov/Pages/doing-bus/eng-consultants/cnslt-rsrces/tools/wiscors/default.aspx

Can i know how to choose the specific autopilot for our application and how much the cost of the such autopilot will come around?

@Rakesh16, that really depends on what you need to accomplish.

You said :

Our goal is to navigate through agricultural fields in autonomous mode using a snake-like zigzag pattern to ensure full field coverage with centimetre-level accuracy.

Would the vehicle path be pre-determined, with the addition of basic obstacle avoidance ?
OR, would the path be decided in real-time based on external factors from various sensors & inputs?
The former is relatively easy with an off-the-shelf autopilot, the latter requires significant integration between systems.

It’s easier for everyone to provide suggestions if you are able to explain the mission in more detail.

@rftop Yes, it follows a predetermined path and stops when it encounters an obstacle. As I mentioned, it moves in a snake-like pattern to cover the entire field. Let me know if there’s any specific information you need to assist further.

One of the most effective means to reduce cost is to be able to do any of this research, analysis, choosing and coding YOURSELF. Or use techical members of your own team.

The mechanics and controls afforded by the vehicle are likely to be most determinative of what controller and actuators will be needed. If you need to interact with the equipment in the field you might need a tablet/laptop, with a screen. The “flight-controller” can be a single-board computer (SBC), perhaps something in the form of an Arduino to something very custom and feature rich, or off-the-self and repurposed from a UAV application.

snake-like = zig-zag

https://ardupilot.org/rover/index.html