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If farmers have such heavy reliance on gps, why not use local positioning systems like AGPS networks? Why are local base stations affected? Do they consistentl

If farmers have such heavy reliance on gps, why not use local positioning systems like AGPS networks? Why are local base stations affected? Do they consistently need satellite gps data? If the satellites go missing for a few days, would that mean local base stations won’t work? I have worked with rtk before, but i never understood why not setup your own personal base station network.

bluGill 2y ago
> i never understood why not setup your own personal base station network. You can, and that used to be common. Some years ago most farmers sold their personal base stations to the local dealer because by doing that the dealer gave their far fields access to a different RTK base station, while before the signals from their personal base station didn't reach the distance fields at all. Plus the dealer maintains the base stations - they are best placed where they are likely to be hit by lightening so someone else taking that risk is overall worth it.
micromacrofoot 2y ago
most people don’t waste money on solving a problem that happens maybe 1% of the time, gps is very reliable
jhayward 2y ago
There are some misunderstandings in the above. 1) AGPS is not local positioning. It is a "speed-up" assist from cellular networks to provide the Almanac (e.g., satellite orbit info) quicker than a GPS receiver can get it from the satellites. All AGPS receivers use the actual GPS satellite signals to calculate the receiver's position. No sats, no position. 2) RTK does not provide a local positioning system. RTK allows a base station receiver, which is in a stable/not-moving site, to observe GPS position calculations over a long period of time and 'averages' the positions to arrive at a highly precise position for itself. It then monitors the real-time positions it calculates and broadcasts a list of error corrections to be applied to the satellite signals to reduce the real-time error, which is constantly changing. Again, no sats, no pos.
- sorenjan 2y ago
  There are a couple of things I wonder about RTK that maybe you or somebody else in this thread can help me with? 1. Where does the kinematics in the name come from? The base station is stationary, and kinematics is about the movement of objects. 2. How does the correction signals work? Is it as simple as "now the position is 3.56 m to the left of the true position, correct your position accordingly", or is it more advanced with detailed timing corrections for each satellite's signal or similar?
  - BenjiWiebe 2y ago
    I'm not an expert either, but I do know it's per satellite, and uses several data points per satellite.
  - bmicraft 2y ago
    How I understand it, RTK comes into play you want to get very precise location on a moving vehicle. To make the location reading more precise you need to take it over some time. To average it while moving you need to know _how_ you're moving. Therefore the need for RTK. The RTK position is then combined with the measured error (measured near that location), because GPS is precise but not accurate enough on it's own. Without correction a stationary point slowly drifts around a bit (accuracy: roughly 0.1-1 meters). The correction is called differential gps, and you can provide it yourself with a base station, or use a service that does just gives it to you (from their network of error measuring base stations), see NTRIP. The accuracy with correction can be greater than 0.01m
BenjiWiebe 2y ago
We do have our own base station for RTK, using a ublox ZED-F9P. It still uses the satellites continuously to calculate the correction data, which the client/rover uses to correct it's own reception of the satellites. Both systems need to be receiving GNSS data all the time. As for planting manually - if the GNSS networks were down permanently or for weeks, then yes steering manually is still possible. If you can wait a day or two and get highly accurate planting and mapping, then why not.

bluGill 2y ago

> i never understood why not setup your own personal base station network. You can, and that used to be common. Some years ago most farmers sold their personal base stations to the local dealer because by doing that the dealer gave their far fields access to a different RTK base station, while before the signals from their personal base station didn't reach the distance fields at all. Plus the dealer maintains the base stations - they are best placed where they are likely to be hit by lightening so someone else taking that risk is overall worth it.

micromacrofoot 2y ago

most people don’t waste money on solving a problem that happens maybe 1% of the time, gps is very reliable

jhayward 2y ago

There are some misunderstandings in the above. 1) AGPS is not local positioning. It is a "speed-up" assist from cellular networks to provide the Almanac (e.g., satellite orbit info) quicker than a GPS receiver can get it from the satellites. All AGPS receivers use the actual GPS satellite signals to calculate the receiver's position. No sats, no position. 2) RTK does not provide a local positioning system. RTK allows a base station receiver, which is in a stable/not-moving site, to observe GPS position calculations over a long period of time and 'averages' the positions to arrive at a highly precise position for itself. It then monitors the real-time positions it calculates and broadcasts a list of error corrections to be applied to the satellite signals to reduce the real-time error, which is constantly changing. Again, no sats, no pos.

sorenjan 2y ago
There are a couple of things I wonder about RTK that maybe you or somebody else in this thread can help me with? 1. Where does the kinematics in the name come from? The base station is stationary, and kinematics is about the movement of objects. 2. How does the correction signals work? Is it as simple as "now the position is 3.56 m to the left of the true position, correct your position accordingly", or is it more advanced with detailed timing corrections for each satellite's signal or similar?
- BenjiWiebe 2y ago
  I'm not an expert either, but I do know it's per satellite, and uses several data points per satellite.
- bmicraft 2y ago
  How I understand it, RTK comes into play you want to get very precise location on a moving vehicle. To make the location reading more precise you need to take it over some time. To average it while moving you need to know _how_ you're moving. Therefore the need for RTK. The RTK position is then combined with the measured error (measured near that location), because GPS is precise but not accurate enough on it's own. Without correction a stationary point slowly drifts around a bit (accuracy: roughly 0.1-1 meters). The correction is called differential gps, and you can provide it yourself with a base station, or use a service that does just gives it to you (from their network of error measuring base stations), see NTRIP. The accuracy with correction can be greater than 0.01m

BenjiWiebe 2y ago

We do have our own base station for RTK, using a ublox ZED-F9P. It still uses the satellites continuously to calculate the correction data, which the client/rover uses to correct it's own reception of the satellites. Both systems need to be receiving GNSS data all the time. As for planting manually - if the GNSS networks were down permanently or for weeks, then yes steering manually is still possible. If you can wait a day or two and get highly accurate planting and mapping, then why not.