I have been researching RTK for several weeks and decided to go with SparkFun products for my project. The guides and community have been a great source of information and education. I have experience in electronics, manufacturing, and software development, but I am completely new to RTK.
I have some land where we’ll be building soon, and I want to set up my own surveying tools so I can locate points. I seem to have started this journey just as new products are being released, which is exciting but also making research a bit harder.
My Goal:
I want to position objects in a CAD drawing of the property, extract their coordinates, and then stake them in the real world–ideally within a few inches. In the future, I would love to explore robot navigation, but my immediate need is accurate point placement.
Planned Hardware:
2x RTK Postcard
2x Portability Shield
2x GNSS Multi-Band Antenna (SPK6618H)
Both setups would be battery powered. One on a tripod to function as the base and another on a surveying pole for a rover. I assume the Postcard’s ESP32 will make it easy to connect to my phone via Bluetooth for the rover side, but I need to decide how to communicate with the base station.
Questions:
Base-Rover Communication:
What is the best way to maintain a stable link between the base and rover at distances up to 1/2 mile?
I like the specs of the “LoRaSerial Kit - 915MHz (Enclosed)”, but I’m not sure if it is compatible with the Postcard. Is LoRa a good choice, or would something else work better?
Portable vs. Fixed Base Accuracy:
Is a fixed base better only because it has a precisely known position, or are there other benefits?
I’ve seen a lot of examples of people placing a base directly above a known point and setting a manual position, but using the rover to hit a known point to calibrate the system would be a much easier workflow because I can set the base in a safe location near the work area and no tape measure or alignment would be necessary.
Would this hardware support that workflow, or would I need to find mapping software on my Android device that can handle the offset automatically?
I would really appreciate insights from anyone willing to help.
What is the best way to maintain a stable link between the base and rover at distances up to 1/2 mile?
WiFi is best, then cellular (you’d need two phones, one for the base, the rover is usually your own phone). If neither of these is viable at your site then yes, a packet radio is the next best option to go 1/2 mile.
Since you’re just getting started, I’d recommend not focusing on the radios for now. Get your Rover/Base working at home with cellular and WiFi, and then move to the internal ESP-NOW radios. They work great up to about 500ft.
I’ve seen a lot of examples of people placing a base directly above a known point and setting a manual position, but using the rover to hit a known point to calibrate the system would be a much easier workflow because I can set the base in a safe location near the work area and no tape measure or alignment would be necessary.
Personally, I would drive a stake or marker at the site. Then capture 24 hours of RTCM, run a CSRS based PPP on the data. That will tell you the exact location of the marker. If altitudes are important, read up on Antenna Reference Points and be sure to subtract your pole length and ARP from your results to get marker’s accurate altitude. Then, store the known coordinates in the base (see Fixed Base mode). Every time you setup on site, put the base over the marker and turn it on. All readings from your rovers should align between days of capturing points. If you want to get really accurate then you need to take multiple days of PPP and compare, throw out any that look off, and average those within bounds.
@Breakfast Another thing to consider is that UM980-based receivers, unlike LG290P-based ones, don’t seem to require much fiddling. If you are completely new to this technology, it might be wiser to go for a device that has mostly functional firmware.
A minimum rover configuration doesn’t require an MCU or a wireless interface (depending on your phone, of course - it has to support serial-to-USB connection over the cable for that to work).
Great advice. I like the idea of just getting the boards to try at home. I had no idea ESP-NOW existed. That sounds great. What does it use for an antenna?
Good idea with putting a marker on the site. In fact, I wonder if I can build a contraption that locks the equipment into place consistently so I don’t have to fiddle with alignment.
I’ll research antenna reference points and some of the other acronyms and learn as much as I can on that path.
Thank you so much for the ideas and concepts to further my research!
just so you know a total station would make a much better job of this and staying accurate. We rarely use GPS for construction staking. With love a land surveyor then you can just live in an assumed coordinate system, don’t have to worry about grid-ground scale factors, etc, etc.
Fixed base works on the principle that you have assigned or known coordinates let says 10000,10000 you can then correct your RTK rover on the fly. You can get the base point very precise as desired but it’s not really necessary because it’s all relative. A lot of surveying is about being relative to other measurements. Whether it’s horizontal or vertical. So do I care that the base point is exactly on state plane coorindates down to 0.01’, no. Do I want point 1000 to be relative to point 1050 by 0.03’, yes. Just some food for thought. Elevations have gotten quite good with GPS but anything that requires elevation we still break out a total station. You could also use GPS and run a dumpy level through them. That would help you increase vertical accuracy.
I had no idea ESP-NOW existed. That sounds great. What does it use for an antenna?
ESP-NOW uses the same internal 2.4GHz antenna used for Bluetooth and WiFi. It’s really handy for small amount of data sent between two points, where BT/WiFi is better for large amounts of data (music, HTTP, etc).
then you can just live in an assumed coordinate system, don’t have to worry about grid-ground scale factors, etc, etc.