Hi, I’m looking into purchasing 2 SparkPNT FPX (one with tilt) to use as a base and rover for on site survey. Before doing so, I had the following questions:
How do you go about “linking” 2 units via the Lora radio included in theses to receive rtk fix on the rover?
I would assume the answer is yes, but can the data logged on the sd cards be used for ppk to be used along the rtk?
For the record, I am quite new to this and most of my knowledge is from what I could find doing research on the internet and asking my friend chat gpt. A base and rover setup with a lora radio seemed the most appropriate for my use case since:
I will be visiting sites in rural areas with possibly a bad connection
Please tell us more about your application. “depth of 500m to 1km” suggests you are using this in a mine?
The Facet FPXT supports tilt and has built-in LoRa. Two units, one acting as Base, one as Rover, will give you RTK positioning. The LoRa has a range of a few miles line-of-sight. The range will drop dramatically for non-line-of-sight.
If your sites are 50km apart, you need a very different solution… Again, please tell us more about your application. Please tell us where your Base and Rover will be located while you are working.
I meant depth as in the length from front to back. The point here is that some of the sites are quite large, which is what led me to searching for a solution with a LoRa radio.
The 50km apart is more so to disregard a permanent base station. The sites which I’ll be working with are most likely too far from each other for that kind of setup. It should function on its own regardless of location. The base and rover will be within each sites limits when doing a survey.
The intended use is general field survey for building and road infrastructure, as well as generating 3d terrain and imagery combined with our drone.
Thank you for taking the time to answer, and sorry for being evidently not precise enough.
How do you go about “linking” 2 units via the Lora radio included in theses to receive rtk fix on the rover?
PaulZC covered most of this, but the nuts and bolts: You enable the radio on both units via the Web Config. Once a device is set to base (via Web Config or serial commands) it will begin generating RTCM and send them over LoRa. The relative accuracy of the base translates to the relative accuracy of the rover: in other words, if you inaccurately tell the base “you are here” but are incorrect by 1m to the west, all readings in the rover will be inaccurate 1m to the west +/- 8mm. For rover/base setups, it’s crucial to get your base setup correct.
I would assume the answer is yes, but can the data logged on the sd cards be used for ppk to be used along the rtk?
Yes, the FP series has a slot for SD logging and can be post processed via RTKLIB or other tools. The FPX will record NMEA, and many other messages including UBX RAWX which can be converted to RINEX as needed using RTKLIB.
Can the new Facet FP be used as a RTK base station for a DJI drone like the Matrice 4? I know the DJI drones can get corrections via Ntrip but I dont really understand if that means ANY Ntrip capable device. I searched in here and google for “using sparkfun RTK as base for drone” but only really found links to other people asking the same thing.
@georgewalter - Welcome! Bast Caster mode is what you are looking for. Our device is setup on the ground, over a known point. It then begins broadcasting a WiFi access point with an IP and open TCP port on 2101. The DJI controller/drone should be instructed to connected to NTRIP Caster at 192.168.4.1 on port 2101. The controller/drone will then start receiving corrections from the base.
Thank you. I’m a farmer not a professional surveyor and I’m just looking for an economical way to make some accurate aerial imagery of my land for my own use. Also would like to start RTK mapping things like underground waterlines, cables, etc. so I can easily find that stuff for repairs or when I’m adding something else in the area. To do that with the Facet I need to also set up a dedicated RTK base station correct? I was thinking about putting it on the roof of my main farm building since I have internet there. Thanks for your help!
The answer is not straight forward. If you have a known location on your land (stake, monument, rebar nail) that you can locate your temporary base over, then you deploy the base over that point for the day, do your work, and breakdown at the end of the day. If you want a permanent base, then yes, you bolt the antenna to the roof, put the RTK receiver inside and it can start broadcasting its data to an NTRIP Caster. This is what I have at my cabin, it’s been connected for years, going down only when the power goes out. I have rough cellular+WiFi reception around the property so connect to my RTK Facet over bluetooth, and I use my phone to get out to the internet to connect to the caster, get the corrections from the base unit in my shop, and I’ve got RTK Fix.
The complication here is your drone. The drone is expecting corrections from the controller’s radio link. The controller connects via WiFi to an NTRIP Caster. I don’t know if the controller can connect to any-ol WiFi or internet connection, or if DJI requires you connect over a local WiFi AP. Base Caster mode is really meant to be a temp thing on a tripod within ~20ft or so of your controller, because the WiFi on the controller is probably limited.
If a DJI can connect to a caster on the internet, then I think the base in the barn is a fine idea. If you have to use a temp base with Base caster mode running, that works too, it’s just a bit more setup.
I set the facet to Base Caster Mode and connected the drone controller to the wifi network it broadcast. In the controller Ntrip settings I put in 192.168.4.1 and port 2101, but it also requires a User, Password, and Mountpoint. Are there default values for these when in Base Caster mode?
If your controller requires it, enter anything it will take. The RTK Everywhere firmware does not check the inbound connections against a ‘good’ user/pw.
I entered “1111” for User, Password, and Mountpoint. By doing this it allowed me to save the Ntrip connection in the drone controllers settings but I was never able to get an RTK fix on the drone. I’ll try setting the Facet up as an Ntrip server via the internet and see if that makes a difference.
I can connect over bluetooth via SW maps to get GNSS service in the app. I can also connect to the Wifi network the unit broadcast when in base caster mode. The unit will not broadcast a Wifi network for me to connect to when in Config mode. I tried using BLESerial nRF, I can connect to unit but cannot do anything other than get to the Main Menu.
I can also connect to the Wifi network the unit broadcast when in base caster mode.
Base Caster mode starts an Access Point style WiFi, which is the same as the config mode, so I’m really confused as to what is broken.
You may want to do a factory reset on the FP just to be sure a setting hasn’t go astray, but if you are seeing that config screen, it is (or should be) broadcasting the ‘RTK Config’ wifi network that you should be able to connect to.
Thank you for the previous answer. I’ve finally got my hands on the unit and have been messing around with it to get familiar.
I now have another interrogation in regards to an available correction source near me which I’m unsure how to or if it can be used (in rtk with a single unit).
This station sends RTCM 3.2 via TCP/IP. Opening up the ip on a browser displays blob of binary being received. I tried inputting the info in the web ui config but I’m unsure if I’m doing the correct thing.
I’ve installed lefebure and can reproduce the steps shown in that gif. But can’t seem to connect lefebure to the gnss unit via bluetooth.
Receiver settings > external via bluetooth > bluetooth device : nothing shows beside disabled.
I have given the app permission while open for location. I’ve tried with the unit connected in the android settings and disconnected. (I have a moto g power 2021 running android 11 if it helps at all)
Don’t know if it is related, but I’ve had some issues at times with connecting to the unit via bluetooth. It would show in the bluetooth settings for pairing, but would disconnect a few seconds after pairing. It sometimes fixes itself after connecting and disconnecting via swmaps for some reason.
@jobina, we have issue with the last version (2026-04-24) of Lefebure. With my two smartphones, I can’t anymore connect devices (RTK Express and hc-05 attached to F9P) to the application. It seems that I’m not the only one. I sent a message to M. Lefebure but didn’t got an answer up to now. In the meantime, I’m using BT_GNSS.
