I snagged a good deal on a Sparkfun RTK Express Kit through ebay. This page will serve as an updating log of setup and discoveries.

My goals for this device is to use it for surveying at my families cabin, and to develope a Wifi Halow radio for correction data.

My family has a cabin in northern Wisconsin. We know where the four corners of the property are, but are struggling to draw straight lines thru the woods. Hopefully this device can help with that. I also would like to make a topographic map of the land.

Wisconsin has a network of correction stations around the state. And they make the service available free ly available. I really appreciate it! It feels like an embrace of the Wisconsin Idea. While the WISCORS network is operated by the states DOT, I’m sure there’s lots of university research that can use this technology.

I signed up for an account, and the next business day was approved with an email showing my login information. The email said they would be sending “connection details for real time network access” in a seperate email. I waited another business day for this email, and then finally wrote them back asking for it. Another form email came soon after with the IP address, Port, NTRIP username, and a redacted password. The port is listed as 2101 and has the following mount points. 

        Here is the list of advanced Network mountpoints currently available:

                        CMRxGNSS        (GPS & Glonass & Galileo & BeiDou)
                        RTCM34  (GPS & Glonass & Galileo & BeiDou)

                The following legacy Network mountpoints continue to be available:

                        CMRplus (GPS & Glonass)
                        CMRplusGPS      (GPS only)

                        RTCM31  (GPS & Glonass)
                        RTCM23  (GPS only)
                        RTCM3Net        (GPS & Glonass)

The network is smart enough to pick the nearest correction station to your GPS, and I think it can even synthesize a virtual base station between points.

Its not a formally documented feature, but according to this Sparkfun thread, if you connect to Port 2102, you can pick the mount point manually from the list of available stations.

The unit came in the mail. I plugged it in, and noticed that the charging light didnt illuminate. It blinked for a second while charging the unit. Reading into it, seems like a dead battery.

Thru SW Maps app on the WISCORS network, Im using NTRIP V2, and mount point RTCM34. CMRxGNSS is some kind of proprietatry Trimble protocol, that only works on Sparkfun Septentrio based modules.

Connected to local Wifi.

Updated firmware from 4.0 to 4.4

Tried BluetoothLE mode, but couldn’t pair and no connection with SW Maps.

Sent a letter to the DOT secretarys office thanking for the WISCORS network.

I looked into buying a replacement battery thru Sparkfun. The battery costs $16, which isn’t unreasonable, but the shipping is an extra $25. This was too much for me. I bought a 1100mAh LiPo battery from Rokland for ten bucks (shipping included!), but when I received it the connector was too small. Looking into it, they advertised a JST connector with a 1.25mm pitch. The RTK Express is supposed to use a JST PH connector with a 2mm pitch.

I bought another LiPo battery thru Digikey. Its “manufactured” by Adafruit, and sold by Digikey. The price of the battery was ten bucks, and an extra $8 for shipping and tax. This one claims to have the right JST PH connnector. We’ll see when it arrives. Still would be saving over twenty bucks.

2/27/2026 – The Adafruit LiPo arrived from Digikey. The new battery fits! The wires are beefier than the Sparkfun battery and its also physically larger, but still fits in the case. Like last time, the unit power up when plugged in, but doesn’t seem to be running off battery power. The charging light isn’t lighting up either. I measured 4.3 volts on the battery test pads while charging. Starting to wonder if there is a problem with the charger controller, or its missing some kind of internal jumper.

I did some reading of Sparkfuns forums, and someone suggested it could be a cold solder join. I measured the test pads again at 4.3 volts. And right next to it, the contacts to the JST PH battery connector were reading 3.8 volts. aha! A soldering problem is likely.

I tried to reflow the battery connector terminals. Plugged it in, wasn’t quite working. But noticed that the charging LED lit up when I was probing the circuit with my meter. Some more probing… not a great connection on the negative lead. Another hit with the soldering iron. Plugged it in, and the charge LED lights up when plugged in!

Updated ZED-F9P firmware from 1.13 to 1.32.

In between updates, I borrowed a survey pole from work, and measured the corners of my families vacation property in northern Wisconsin. I still need to learn more about surveying, because benchmarks are 25 to 30 feet off from my readings. I think its because QGIS is set to the default projections settings.

I bought a 1.8 meter, four piece carbon fiber survey pole off ebay. Seems like it was drop shipped from China. I’m very happy with it! It fits in a carry on. I also bought several cellphone bike mounts, and these are the ones I am currently using. The RTK surveyor gets clamped on with this. And my cellphone with this.

I spent a Saturday morning walking around an old Nike Missile base with my new GPS pole. I was delighted to find an ACOE benchmark on the property. One of the properties corners has a square concrete monument that also brings me joy.