From GPS to GNSS: What are the Challenges of Running a GPS Network – now and in the future?

This is part 3 of a 3-part blog.

Managing California’s largest commercial GPS network is a huge challenge – now and for the future.

In this third and final blog conversation, CSDS President Tom Cardenas and Systems Administrator Ed Morrison talk about the challenges of a network that covers 93,000 square miles in a geography that’s anything but standing still.

Q: What are the challenges of managing this GPS network?

One thing we discovered by running a GPS network in California is that we’re probably the most unique geography to manage a network in. What California is pretty famous for is the fact that we have multiple tectonic plates moving in different directions, at different speeds. Then with the water problems and the drought we’ve had in California, depending on how much water is pumped out of the ground or just disappears because of the drought conditions, we start to see a lot of rapid movement vertically with the ground.

So we have these reference stations fixed all over California – well, the reference stations are fixed but the ground’s not. It has become a challenge for us to manage such a large network with so much movement.

ED: I would say it’s a challenge for anybody trying to run a network. In order to deliver high accuracy to your customers, you need to have all your stations in an exact position and not moving. The problem is we’re in California, so the stations move.

TOM: I can say with confidence that we’re the only provider of this type of service that realizes how much California is moving. We’re getting everything back to where it needs to be in one of the most challenging geographies to operate and manage a network. California is moving up and down, left and right, at a pretty rapid pace. And we’re doing everything we can to keep up with it.

We try to make this as convenient as possible for our customers, but it can cause some disruptions to their workflow. They need to ensure they’re utilizing best practice in the field – checking into known locations with the rover and doing a site calibration. Essentially, a site calibration is a rotation and a scaling to a known network of points. If we ever perform adjustments on our network, meaning that there’s a potential for a slight change in the positions that are being broadcast from our network, we tell our customers they will need to do a site calibration.

Q: What does the future hold?

It’s just amazing to see how rapidly the technology is evolving. It’s smaller, faster, more affordable and typically easier to use and administrate. But I think that with the nature of the movement in California, until there is a purely satellite-based correction system, things will be affected by the tectonic movement of the plates. Until we get to the point where you’re getting your corrections from a satellite signal with a versatile and dynamic real-time correction system instead of using a cellphone to receive these corrections, there will be issues. In other words, we almost need a satellite to be a reference position for this to really work well.

The only problem is, with the satellite-based correction technology that’s available now it can take a minimum of 15 minutes to do what we call an initialization. That’s how long you have to wait to start getting that correction at the highest accuracy achievable at this point, which is about 10 centimeters in three dimensions. That’s fine if you can wait 15 minutes to get that 10-centimeter precision. But once you lose lock or visibility between your antenna and the minimum number of satellites for a fixed position – say you go under trees or you experience any obstruction between the receiver and the satellite – you’re back waiting for another 10 to 15 minutes to get yourself reinitialized.

On the other hand, when using the GPS network – with a decent view of the sky and cellular coverage – you’re connected instantaneously and you’re down to 1-centimeter accuracy horizontally, and about 2 centimeters at the most vertically, within a matter of seconds.

For those who’d like to see the advantages of our GPS network for themselves, we offer a free 5-day trial subscription to the CSDS RTN, the leading GNSS Real-Time Network in California:

I encourage everyone to try it out and compare it with their current solution to get a better idea of what they can gain from our services, including more reliability, more coverage, and more accuracy. It’s a risk-free opportunity for your company to reduce hardware costs by up to 50% while achieving the same or better level of accuracy in its precision surveying & mapping applications.

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