The Dawn of a New ERA in GPS Accuracy

June 1, 2010 By: Eric Gakstatter

Last week, as you may have heard given the multiple launch delays, the United Launch Alliance (a Lockheed and Boeing joint venture), under contract with the US Air Force, successfully rocketed a new GPS satellite into orbit.

The GPS satellite launched into orbit last week wasn’t just any other GPS satellite. It was the first of a new generation of GPS satellites that are going to change the way geospatial information is collected and processed in the future. Its new features are going to profoundly transform the geospatial industry. I’m not exaggerating.

Here’s why.

The new L5 signal will eventually (when it’s being broadcast from enough satellites — more on that later) significantly transform GPS receivers in two ways:

It will result in high-accuracy GPS receivers being much cheaper and smaller.
It will make collecting high accuracy geospatial data much more convenient for the average user.

Let’s examine in more detail.

Why will high accuracy GPS receivers be cheaper and smaller?

Today’s GPS dual-frequency receivers (L1/L2) can achieve a high level of accuracy (1 cm) in a short period of time, as little as a few seconds. But, they are expensive. An entry-level GPS dual-frequency receiver is a few thousand US dollars. The primary reason is because there is a limited number of companies that design GPS dual-frequency receivers for the geospatial industry, maybe a dozen or so. Why is there a limited number of manufacturers? The answer is because the original L2 was not an open signal. In the 1980s, some very smart engineers figured out how to utilize L2 (designed for military use only) in commercial receivers. When they developed those techniques, the companies were smart enough to patent them. There are so many patents in place that it makes it difficult for a new designer to enter the traditional GPS dual-frequency market, whether it’s surveying, machine control, GIS, or whatever.

Unlike the original L2, L5 is an open signal. Its specification is published for anyone to use. No license fee. No receiver tax. Nothing.

Without any patent blocks, any company in the world is free to develop a GPS dual-frequency (L1/L5) receiver that would be just as accurate, and arguably more accurate, than today’s L1/L2 GPS dual-frequency receivers.

Looking back at the history of electronics, within and outside the GPS industry, we know that increased competition usually results in lower prices to the consumer and improved product quality.

Take, for example, GPS L1 receiver chips used in personal navigation devices and mobile phones. Those chips are available today for less than $3 each. Fifteen years ago, much less powerful GPS L1 receivers were $200 each and 10 times larger.

Mark my words; you will see a similar trend with high-accuracy GPS dual-frequency receivers. GPS dual-frequency receivers will be sold at prices you can’t imagine today, allowing geospatial professionals (and an educated general public) to collect high-accuracy data (horizontal and vertical) inexpensively.

The only thing holding this trend back is the availability of L5. It needs to be broadcast by about 24 GPS satellites. That’s going to happen somewhere between 2018 and 2020. Of course, GPS designers will be working on their receivers long before that.

Why will collecting high-accuracy geospatial data be much more convenient for the average user?

First of all, the cost of high-accuracy GPS dual-frequency receivers will plummet significantly due to the open L5 signal. This will spur a fantastic amount of innovation and competition among a large number of receiver designers, especially in the consumer electronics market. In the geospatial industry, we will benefit greatly from the consumer electronics industry because the high volumes in the consumer market will further spur innovation and cost reduction.

Oddly enough, at that time, the most expensive part of a high-accuracy GPS receiver for geospatial professionals may be the antenna. The consumer electronics market won’t accept the type of high-accuracy GPS antenna we need (too big/bulky), so the limited number of antennas for the professional geospatial user means you’ll pay a higher price; maybe a $100, maybe $200.

If you have a minute, you might want to browse this article by Dr. Frank van Diggelen. Essentially, he says that consumer GPS receivers in your mobile phone, PND, etc. can be as accurate as a GPS receiver built for high-accuracy surveying. The reason they aren’t, he says, is due largely to the inferior antenna being used. Now, I’m not saying I buy everything he’s writing, but he’s a lot smarter than I am with regard to GPS, and I do have enough experience to know that antennas can make a big difference in receiver performance.

What you’ll see, eventually, is GPS dual-frequency (L1/L5) receiver technology in consumer electronics, which means high-accuracy positioning at consumer prices. Take it a step further and one can make the statement that high-accuracy positioning will be in the hands of the consumer. A knowledgeable geospatial professional will be able to take a very low-cost, high-accuracy GPS dual-frequency receiver and collect (or have others collect) an amazing amount of valuable geospatial data (think high accuracy vertical) that was otherwise too expensive to collect using today’s technology. That is where we are headed, guaranteed.

Wildcards

Other GNSS

The time-frame estimation I made above (2018-2020) for a full (24-satellite) constellation of GPS satellites broadcasting L5 is based solely on the activities of the U.S. government. Keep in mind that the U.S. government can’t exceed the 2020 deadline because December 31, 2020, is when the U.S. Air Force says they’ll stop supporting legacy GPS L1/L2 dual frequency receivers. So, the end of 2020 is the worst-case scenario.

Of course, the the U.S. isn't the only country working on GNSS. Europe’s Galileo system also utilizes L1 and L5. It’s possible that in the 2014 timeframe, the U.S. could have a dozen GPS satellites broadcasting L1/L5 and Galileo could have a dozen Galileo satellites broadcasting L1/L5. Because the U.S. and Europe have been working so closely together to ensure GPS and Galileo work together seamlessly, having 12 Galileo satellites broadcasting L1/L5 is the same as GPS broadcasting L1/L5.

China is also working on a GNSS called Compass/BeiDou. Although they are tight-lipped with their intentions, it’s possible they could launch some satellites in orbit that may contribute to an L1/L5 solution, but China is a serious wildcard.

L2C

Some of you may be wondering why I haven’t included GPS L2C in the discussion. L2C is an open GPS signal much like L5. There are currently seven GPS satellites broadcasting L2C. Not including Galileo, there will be 24 GPS satellites broadcasting L2C before there are 24 GPS satellites broadcasting L5. In fact, there may be some designers who decide to develop L1/L2C receivers. However, Galileo isn’t supporting L2, so while there will probably be triple-frequency receivers (L1/L2C/L5), my guess is that the standard will be L1/L5 because the third frequency isn’t going to buy you much.

Conclusion

No other conclusion can be drawn but that in the future, as soon as 2014 and as late as 2020, high-accuracy GPS receivers (cm-level in both horizontal and vertical) will be in the hands of anyone with a few hundred dollars to spend. This will be consumers as well as professional geospatialists. Professional geospatialists will have easy access to a fantastic new tool that will allow them to collect high-accuracy horizontal and vertical data, at a very low cost and very conveniently. I keep referring to vertical accuracy because accurate vertical data is much more expensive to acquire with the technology that exists today, GPS and otherwise. Not so in the future. When one really thinks about the value of accurate low-cost vertical data, the numbers of applications are mind-boggling and will certainly send the geospatial industry in a new direction.

Free Webinar on June 24th

On June 24th (was originally scheduled for June 22nd), Geospatial Solutions will be conducting a free 60-minute webinar, moderated by me, on "GIS Mapping for Forestry, Agriculture, and Other Natural Resource Professionals." I will discuss GIS mapping software tools/concepts/techniques as well as GIS mapping hardware such as GPS receivers, digital cameras, and laser rangefinders. Although focused on natural resources, it will be relevant for all people interested in GIS mapping, which could be utility companies, municipalities, transportation organizations, etc. Sign up now by clicking here and submit questions in advance.

Thanks, and see you next week.

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