Centimeter-level RTK Accuracy More Available for Less

Reposted from GPSWorld

Last month, I started off 2014 with a bang by listing all the public RTK bases available in the United States, most of them being free. I received a lot of positive feedback and some enlightenment. For example, I didn’t know that in California, there are more than 330 RTK public base stations accessible by anyone for free via the California Real Time Network website at the University of California at San Diego! What a tremendous resource for California surveyors and GISers.

Remember that RTK will give you 1-2 cm accuracy horizontally and twice that for vertical. If you know that and also know that there are 330 free RTK bases in California, why would anyone use post-processing for high-precision (e.g., sub-foot) GIS data collection? RTK technology used to be reserved for people who could spend tens of thousands of dollars on a GNSS receiver. Not any longer. RTK receivers are available for under $7,000, and you don’t need to invest in a RTK base unit if you’re in range of a public one on my list (or a commercial one not on my list).

I’m pretty sure it was Charlie Trimble (founder of Trimble Navigation) who said “accuracy is addictive.” It sure is. Once you experience real-time centimeter-level accuracy (RTK) in the field, you won’t be satisfied with anything less, and neither will your GIS.

I’ll keep updating the List of Public RTK Base Stations in the U.S. as people continue to inform me of ones that aren’t on my list. If you know of one, please email me.

Keeping on the subject of RTK, 2014 might be the year of inexpensive RTK receivers. Whereas today you can find L1/L2 GNSS RTK receivers (in the U.S.) ranging from US$6,500 to US$25,000, there are rumors that some manufacturers are going to break through the US$6,500 price point.

This is in line with the prediction I made a few years ago, but for a different reason. In 2010, I wrote that RTK receivers would become very inexpensive due to the new L5 signal being introduced, which would increase competition among GNSS receiver designers. I speculated that with more competition, the selling prices would significantly decline. Well, we are still without a usable L5 signal (although making progress) due to the slow deployment of modernized GPS satellites and the delay in Europe’s Galileo system, but we are still seeing a steady decline in the price of RTK receivers. Why is this?

Even though there are a limited number of designers of RTK GNSS receivers, an increasing number of companies are buying RTK GNSS boards from these designers and making their own finished RTK GNSS receivers that look and perform very similar to receivers available today, for a fraction of the price. This is especially true in China, where there are several manufacturers buying RTK GNSS receiver boards from Trimble, Novatel, Hemisphere et al, making their own finished products and selling them. They were initially selling to very price-sensitive markets such as Africa, but now you see them setting up distribution in North America.

This “OEM Syndrome” has put tremendous price pressure on existing brand-name RTK GNSS receivers as the Chinese-equivalent products are priced as little as 25% of the equivalent brand-name products. Of course, this drives the leading brand-name companies crazy. They are forced to either drop their price or otherwise convince buyers that their products are worth a significant premium. During these times of tight capital budgets, it’s increasingly difficult to do the latter. When enough satellites are in orbit broadcasting the L5 signal, you’ll really see this effect gain traction because there will be a lot more RTK GNSS designs to choose from, and the result will be better quality. More competition always results in better product quality and performance.

The fact is that RTK receivers are moving towards becoming a commodity. As much as your local salesperson would like you to think they are selling a better RTK GNSS receiver, the technology gap between leading-brand designers and others is closing and probably unnoticeable to most of you. The major differences end up being the quality and reliability of the finished product (system design, battery, display, antenna integration, power supply, etc.). Having a great RTK GNSS receiver board inside is useless if the system design is unreliable.

More Real-time PPP Competition
For the longest time, it’s only been OmniStar (now owned by Trimble) and Starfire (owned by Deere & Co.) in the L-band high-precision correction game. Then, last year, the International GNSS Service announced its free decimeter real-time PPP service.  The catch is that receiver designers must incorporate IGS firmware to make use of the signal and…it’s only an Internet-based service (no satellite communications).

In the past couple of months, Hexagon (which owns both Leica and Novatel), made a bid for Veripos. Veripos operates an L-band GNSS correction service for the oil and gas industry. Last year, TerraStar, a subsidiary of Veripos, announced its new decimeter service that is very similar to OmniStar and Starfire. It uses satellite communications for a data link. Altus Positioning Systems incorporated the TerraStar service into its receivers. Hexagon is very close to closing the deal with Veripos and just last week announced a partnership with competitor Topcon Positioning Systems. The result is that Leica and Topcon both will start offering high-precision L-band GNSS correction services with their receivers. If you’re an L-band decimeter user, this is probably good news for you. More competition = higher quality and lower price.

Thanks, and see you next month.

~Eric Gakstatter

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