RTK over wireless hotspots without static IPs

Jim White

Hi All, due to my frustration with the cell phone companies over their need for static IPs to allow connections from external sources, I did some experimenting and have found the following work around (for the technologically adventurous people out there)...

This is specific to using a RTK base that is connected to a wireless hotspot.

In the normal method, the RTK base (in my case a T2) acts as a TCP server, and waits for a TCP client (in my case a LS RTK rover) to connect and receive the correction data.

The problem: Both Verizon and ATT wireless systems have a form of firewall between their networks and the internet, and it does not allow external connections to ports of normal dynamic IP address that are assigned each time a hotspot is turned on. The external connection is needed by the RTK rover to receive the corrections. The wireless companies do allow the external port connection if you purchase a static IP address from them.

The solution: The wireless companies allow the transmission of data over the dynamic ports to an external IP address and port. For this solution, you need access to a router that is connected to a cable modem (in my case Spectrum cable). Google "what is my IP" from a PC connected to the Spectrum router. Also note the PCs internal IP address.

1. The RTK base is probably already configured as a TCP server. Using netview, you can add a another configuration as a UDP transmitter, sending data to the Spectrum router IP address and an unused port on it (the "UDP port").

2. On the Spectrum router, allow port forwarding for both the "UDP port" and another "TCP port" to the internal IP of the PC.

3. You will need software for a "UDP to TCP bridge" on the PC. I found a freeware package on "Joshua AIS Wiki". Download it, unpack it into a directory on the PC, configure the XML file to your "UDP port" and "TCP port", and then leave the program running on the PC. It is a rather old school user interface, but functional. No bugs or mal-ware were detected by my PC. Some people may consider this a security issue.

4. On the rover, make a new general profile for a TCP rover and connect it to the Spectrum router IP address and "TCP port". Now it can be used as normal.

General notes: my Spectrum router is a residential connection with a dynamic IP. My IP has not changed in the past year, but if it does, both the base and rover would need to be updated. I check my IP before each field session.

This method doesn't affect any previous of configuration of the base or rover, so can be used in parallel with other methods, allowing for redundant field solutions.

This has been running flawlessly for me, and I hope it does for others as well. If anybody finds a better way to do it, please let us know.

Jim White