@hTo137 Thanks! Can you explain/discuss how the telemetry might (or might not) work? I’m intrigued! Sounds kind of plausible with two SDRs working together.
My explanation may fall under the “might not” work category. But you gotta know where the TaterBot is at any given time* and you may need to tell it where to go. So it will send location updates, plus whatever other pertinent data that potato fields possess. But (I know Lime will hate me for this) you might be able to use an old cell phone on Taterbot instead of a LimeSDR. Oh, make it solar and compressed-air powered. Compressed air for cloudy and night time operations with compression via solar power.
Maybe, out of potato, season TaterBot becomes SentryBot or perhaps outfit for another crop.
*
You don’t want TaterBot becoming enthralled with the electric vehicle for example and wandering off.
Have you come across the 'Weedinator’ project? It uses two GPS modules, one as base and the other as rover to achieve error cancellation.
No had not seen that. I’m not sure but I guess error correction and accuracy/precision are one and the same in regards to GPS.
There are a lot of interesting projects on hackaday.io.
###Update: That’s your project, nice! You really dislike weeds. 
If you’ve just got a rover, you have no idea if the movement the GPS is reading is the movement of the machine or the errors incurred through clouds, humidity, ionisation, cosmic rays etc … Unless there is a reference GPS unit not too far away that stays still and has mostly the same errors. If the reference GPS was too far away it would have different errors.
It’s a bit of a brain teaser! But it seems to work.
If there was a better system using local triangulation rather than satellites that would be much better so to think the LimeSDR could do this is not altogether farfetched 
Nowadays you could also augment with an inertial guidance system. Seems like gyros are in everything now…phones, game controllers, etc. Might prove difficult but unsure.
But your idea of an LPS (local positioning system) is good. TDOA (time difference of arrival) type setup might suffice. That what you mean by triangulation?
I was initially suggesting GPS and then also suggested an intertial guidance augment for bad GPS reception. But you mentioned a local triangulation setup.
But now another thing that came to mind, what GPS satellites are flying these days? There may be others up there. I know there’s GLONASS. Other countries are putting up their own too. Centimeter accuracy is wanted/needed for cars/trucks/planes/plows/tractors/boats.
Yes there are other satellites appearing such as the Galileo, but it’s not working yet. Also it is becoming increasingly easy to put that lights up into the sky so before long there will be hundreds of thousands of them.
In the meantime, as far as local triangulation is concerned, I have a idea. This could very well actually not work though.
There is one Rover and a number of base stations in a field. The Base stations send out to signals simultaneously, one at 50 kHz (ultrasonic) and the other at 2 GHz (rf).
The first signal is slower than the second, so the second signal arrives first and acts as a kind of stop watch, telling the rover to expect a 50 kHz signal very soon. The time difference between the two signals is proportional to the actual physical distance . Make adjustments for humidity, pressure and temperature and now do a triangulation and we might have an accurate fix to less than 1 cm? Any comments?
Can’t say much about your idea, except it sounds like extra work to me. Here are some other thoughts.
We are bathed in RF, wifi, cellular, gps, glonass, am,fm,uhf,vhf, etc.,etc. So why not make use of that, even if only passively. It’s free!
The other thought goes back to the original idea I proposed sort of and is here:
I only read that blurb and haven’t looked past that but it sounds promising but looks stalled. But maybe it’s working.
Nice find, thumb up…
Repeater question.
I am not versed in cell phone technology but it seems to me that the repeater should function by receiving a DL signal from a tower, say LTE channel 2, then re-transmit that same signal locally on some different channel, say 3. The phone would have to know to tune to channel 3 and send back a signal on UL channel 3. This has to be received on the repeater and re-transmitted back to the tower at UL channel 2.
The tower is fixed at a certain channel, right? What decides the phone’s channel? Would the above scenario “just work”?
@Axeman … I don’t think the phone will receive on any frequency other than a strict set defined by the operator ie AT&T, Vodafone et al. What you have described is still possible, but you’d use 2 repeaters working one after the other and the phone always works on it’s set frequency:
Say you wanted to get a 4G signal around a building with thick stone walls - you could blast the whole thing with a high powered signal and fry the brains of anybody near the transmitter, or have a network of repeaters flip flopping frequencies/channels so that they did not feed back with one another, each working at relatively low power. The first repeater would receive on channel 2 and transmit on channel 3, the next receiving on channel 3 and transmitting on channel 2. Of course, I could be talking total nonsense, but it’s an idea I’ve had in mind.
So if channel 2 and 3 are both within the phone company’s set of allowed channels then the simpler repeater should “just work”, it would seem. The phone would just lock in on the stronger channel. There may be some ID encoded on the signal that says it can only be from that one center frequency. I will make a test, as soon as I find out what frequencies are involved.
@Axeman … it would be interesting to try it. I noticed that my operator, ‘Three’, uses band 3 and band 20 here in the UK for 4G so in theory my phone should be ‘programmed’ to accept these frequencies. In day to day reality it just uses band 20 as there’s no band 3 base transmit where I live.
PS. It’s not too difficult to get the LimeSDR to upconvert / downconvert.
@hTo137… greetings, the github stuff relates to rtk-sdr and use of rtl-sdr usb modules for GNSS… (gps navigation)
NASA is upgrading GPS constellation, this or maybe the following year to support an additional RF band, similar to military…military is using 1.2GHz along side the civil 1.5GHz, it allows to compensate for the ionospheric interference, hence drastically increasing the accuracy of the navigation. Military band is encrypted, cant use it… but now there will be a second civil band which could allow the same. So hence i was thinking either use two phased sync rtl-sdr’s or a limesdr, the difficulty is to adapt the current GNSS sdr lib to support the new channel standard.
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That great news for the weedinator project . Saves us the expense of launching our own satellite etc.
If I had to guess someone has probably already worked out the problem and hasn’t put it out there or it’s out there and not prominently displayed. Those rtlsdr dongle really are (were?) a boon to the advancement of SDR. I come across many projects written just for those devices*. It wouldn’t surprise me to learn the solution’s there or very close. Sometimes github searches turn up interesting things. 
[details=*]If only there was an SDR API already in place then all that rtlsdr dongle code would have been usable with other hardware. See
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