Comments: What is GPS RTK?

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  • The article is excellent. However it is a little nebulous when it comes to pushing the RTCM data. I am using Ubuntu 18.04 and have installed SNIP NTRIP Caster to be able to push the data. I do not understand how I am suppose to use processRTCM() to push the data to the serial port so that SNIP can parse it and cast it so the rover can pick it up. Since all of the above is free software an example using it would be fantastic. There are unfortunately no UNAVCO SNIP servers near my school and I bought a 2nd ZED-F9P assuming that it would be great to set up a base station. I was dissapointed that the tutorial ended before actually establishing a way to push the RTCM data to by rover. When I run the example in the tutorial above the survey completes and the LED says that RTCM messages are being produced but I do not see any info being printed in the serial monitor (e.g. no pretty print of the hex data. I am assuming that there should be data and that I should be able to have another program monitor the serial port and send that data elsewhere, such and the SNIP NTRIP Caster.

    • Thanks! This tutorial is the general one on RTK. Be sure to checkout the hookup guide for the ZED-F9P, specifically how to setup it up as a correction source. Looks like you've read it. Once RTCM is being output you should see pretty print. Something else must be going on. I recommend using u-center to check the status of the survey in and see which ports are enabled for RTCM output (I2C should be by default but perhaps it got changed).

      I am assuming that there should be data and that I should be able to have another program monitor the serial port and send that data elsewhere, such and the SNIP NTRIP Caster.

      Correct. Once you have processRTCM() working, you're getting really close.

  • Have you messed around with setting up a second -2 as your base station at all? I know ublox evaluation kit uses two -2 modules for correction.

    • Yes! It's pretty easy to do. We provide some example sketches in our GPS-RTK Library. As long as you've got a clear view of the sky it takes about 5 minutes for the module to get a really accurate (sub 1m) location lock. The NEO-M8P-2 then begins outputting RTCM correction data.

  • a minor error: "about 20km or 12,000 miles away.". I think you mean 20,000km.

  • Thanks for the SNIP product mention, a few details to provide back to you in case you want to update it.

    The open caster you mention in the article is mostly used by our SNIP evaluation users as first place to get corrections when they initially power up. What you perhaps should mention in its place is our public open Caster at RTK2go.com [uses port 2101 like most NTRIP) where we allow ANYONE to send corrections to it, and then on to any other users anywhere in the world. [try rtk2go.com:2101/SNIP::STATUS for a real time summary]. A great many of the folks that use this are in fact using uBlox for L1-only RTK work. The SNIP product is a professional grade NTRIP Caster with neatly a thousand nodes now deployed, the RTK2go site just uses a copy of that. But it is the free "Lite" version of SNIP that is just what you prouser community may want. In fact the RTK2go.com project was started simply because many people could download our free products but could not also get a free static IP to publish from.

    Our firm was founded on the belief that RTK was a public right and a commodity, not some arcane art only for the high priests of GPS. SNIP was created to advance that. Love your firm, the lab it full of employee buys of your stuff for quick prototypes. Regards,...


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