RTK or PPP? Let’s Talk About What You Actually Need on Site

One question I hear quite often from surveyors is:

“Can this GNSS receiver do PPP?”

And honestly, it is a good question.

But after years in the field and talking with surveyors about the equipment they use, I have noticed we sometimes ask whether a receiver can do PPP before asking whether PPP is actually what we need for the job.

So, let’s talk about it the way we would talk about it on site.

RTK is probably what you are already using most of the time.

You arrive at your site, set up your GNSS rover, connect to your CORS network or base station, get your corrections, and you are ready to work. That is RTK.

And when the correction link is good, RTK is fast and gives you the real-time accuracy you need for a lot of everyday surveying work.

Boundary surveys. Topographic surveys. Construction work. Setting out. Road projects. For these kinds of jobs, RTK is usually the practical option.

So where does PPP come in?

Now imagine a different kind of job.

You are working somewhere remote. The CORS coverage isn't good. Internet connectivity is unreliable. Maybe there isn't a convenient reference station to work with.

This is where you start looking at PPP (Precise Point Positioning).

PPP doesn't depend on a nearby base station in the same way RTK does. Instead, it uses precise satellite information and correction services to improve your positioning.

Sounds perfect, right? Well... not so fast.

PPP has a trade-off.

One of the biggest differences you will notice in the field is convergence time.

With RTK, when everything is working properly, you can get your fixed solution very quickly. However, with PPP, you may need to wait for the solution to converge before you achieve the accuracy you are looking for.

And that matters.

If you are on a construction site and someone is waiting for you to set out points, you probably don't want to spend unnecessary time waiting for a PPP solution when you already have a reliable RTK correction.

But if you are working in a remote location where getting RTK corrections is difficult, that waiting time may be a reasonable trade-off.

So which one is better?

This is where I think we sometimes get it wrong.

RTK isn't better than PPP. PPP isn't better than RTK.

They are simply useful in different situations.

If I have good CORS coverage, a reliable correction connection, and I need to get my work done quickly, I'd go with RTK.

If I'm working somewhere remote where conventional RTK corrections are difficult to obtain, then PPP becomes much more interesting.

And about that question: “Does this receiver support PPP?”

Don't stop at a simple yes or no.

Ask:

What correction method does it use?
How long does it take to converge?
What accuracy can I realistically expect?

Because two receivers can both advertise “PPP capability” and still offer very different experiences in the field.

At the end of the day, the goal isn't to have a GNSS receiver with every feature available.

The goal is to have the right positioning method for the job in front of you.

And sometimes, the best answer to “Should I use PPP?” is simply:

“What are you trying to achieve on this particular site?”