Survey Perspectives – Early March 2008

March 5, 2008  - By 0 Comments

Catching Up

There has been a lot of activity on both the civilian and military sides of GPS/GNSS these past few weeks. Instead of a central theme to this newsletter, I’m going to comment on three points of interest: a DoD directive regarding position, navigation, and timing; PRN32; and some new product developments.

New Department of Defense Directive

On February 19, 2008, the Deputy Secretary of the U.S. Department of Defense (DoD) issued Directive #4650.05, which addresses, among other things, the “policy, procedures and responsibilities” for GPS. Although there will be many who will dissect and analyze the Directive for weeks to come, it’s clear that civilian influence on GPS continues to rise. You can read our Military and Government Editor Don Jewell’s initial comments here.

Of interest to the survey/construction/mapping community is the fact that the Department of Transportation is specifically mentioned as a key external agency (external to the DoD) to have a say in GPS activities. The Department of Homeland Security and NATO were the other two key external agencies named.

There is nothing earth-shattering about the directive, but it certainly sends a strong message that the federal government wants the civilian community — domestic and perhaps more so, international — to feel more comfortable about GPS, even though it’s still a U.S. military program.

PRN32

After a few months of waffling and discussion and announcements, PRN32 was finally set healthy. It’s been ready to go, but there has been concern about the effect that it would have on GPS receiver firmware. It was suspected that some GPS receivers wouldn’t be able to handle it, or would be adversely affected by it, because they may interpret PRN32 as PRN00.

This isn’t the first time that DoD has used PRN32. PRN32 was used temporarily in the early 90s until it was discovered that some GPS receivers interpreted it as PRN 00. It hasn’t been used again until now, some 15 years later.

Chances are that your receiver should be able to handle PRN32, given the event back in the early 90s and the DoD memo released more than a year ago. The satellite in question was set healthy on February 26, 2008. If your receiver is tracking but still not using PRN32, it may be worth a call to the dealer or manufacturer of your equipment to see if there is a firmware update available.

Depending on your location, PRN32 may help you. I was in the field in the western United States a couple of weeks ago, for example (before PRN32 was set healthy). I was only using five GPS satellites with an RTK receiver while down in a hole, and my receiver was tracking PRN32. It was in a perfect part of the sky that would’ve probably allowed me to get the tough shot I wanted, had it been set to healthy at that time, but no dice. I’m going back to the same site in a few weeks, and I’ll be watching for it. The RTK receiver I was using is more than 10 years old, so it will be interesting to see how it handles a healthy PRN32.

Product Announcements

Normally, I leave the new product announcements out of the editorial area, but three recent ones deserve particular attention. I mentioned two of them, from Javad GNSS and Magellan, in my December column of who to look out for in 2008. Both companies have come through in short order.

Javad GNSS. Early last month, Dr. Javad Ashjaee — former Trimble engineer and founder of Ashtech, Javad Positioning Systems (which was sold to Topcon in 2000), and Javad Navigation Systems — introduced the world to products developed by his new venture: Javad GNSS. In true Javad style, he’s pushing the envelope on both the technical side and the business side of the equation.

Of course, it’s expected that Javad’s new product line would account for every signal available, and probably every one that is planned. No disappointment there. His Triumph technology sports 216 channels to track everything from GPS L1/L2/L5 to Europe’s E1/E5 Galileo to GLONASS L1/L2, as well as all SBAS signals. That’s no big news, though, as all the other major manufacturers offer similar products.

What’s new and unique about Javad’s offering is the “RTK Umbrella.” The concept makes sense. The idea behind the RTK Umbrella is to increase the reliability of RTK positioning. A cluster of four antennas (on the rover) is used to compute sixteen baselines for every RTK measurement. Here is what the umbrella looks like.

After looking at it, you’re probably thinking the same thing I am: How am I going to cart that thing around all day? The short answer is, you won’t. But I can see an application where one could use the RTK Umbrella for setting control and performing other geodetic functions that require a higher degree of reliability and integrity. Then, you could toss it into the back of the truck and just use the single antenna for the production work.

It’s an interesting concept. I’ve got to give the guy credit for being creative.

Magellan. Magellan has been noticeably quiet in the high-end, survey-grade survey business for quite a while. The roots of their high-end business came from Ashtech, which they acquired many years ago. Yes, they have the Z-Max.Net that they announced a couple of years ago, but in a world where multi-constellation GPS and GLONASS receivers are the norm, it’s a me-too product at best. To give credit where credit is due, Magellan has continued to dominate the lower-end L1 survey-grade receiver market with its ProMark series of receivers and more recently, its ProMark 3 RTK product.

Now, as the company has been threatening to do (albeit under its breath), it has placed both feet squarely back in the high-end survey receiver business with the ProMark 500, a multi-constellation receiver that places Magellan in the same class as the best Trimble, Topcon, and Leica receivers. Granted, there is not a lot of information available on the ProMark 500, other than the video on its website. The real test will be when Magellan starts to ship the product, and dealers and users begin to run it in production mode.

My guess is that the technology will be pretty good. I think one of the biggest challenges will be to rebuild their surveying distributor network. With Topcon and Leica buying up distributors like candy in the past twelve months, the pickin’s are getting pretty slim.

Trimble. Remember when the Trimble ProXRS was the cream of the sub-meter mapping crop of receivers? It was a L1 C/A code workhorse of the past decade around the world. Then, it faded away when the ProXT/ProXH receivers were introduced. But neither of those really replaced the ProXRS.

Now, Trimble has upped the ante by introducing the ProXRT. The ProXRT offers users a range of accuracy depending on their needs, from sub-meter down to decimeter (10cm) accuracy. Perhaps the most significant feature is that the ProXRT is capable of using the Russian GLONASS satellites as well as GPS. The product announcement implies that GLONASS signals are used when GPS satellite availability is impaired. I have two comments about GLONASS on mapping-grade receivers.

    1. Unless you are using your own GPS/GLONASS reference station, the GLONASS signals used on a mapping-grade handheld will be uncorrected (autonomous). Virtually no CORS receivers have GLONASS capability; neither NDGPS nor WAAS/EGNOS use GLONASS. So, there are no free public correction sources for GLONASS like those we are used to with GPS. However, many RTK networks are broadcasting both GPS and GLONASS corrections.

 

  1. Autonomous GLONASS measurements offer much worse accuracy than autonomous GPS measurements, by a factor of five. This is because of the inferior clock and ephemeris data.

However, if used in the right circumstances, tracking a GLONASS satellite(s) can be the difference between getting a measurement or no measurement at all — even if the accuracy of the position takes a hit.

Another feature that the ProXRT brings back, which was curiously missing from the ProXT and ProXH, is OmniSTAR capability. The ProXRT is capable of using OmniSTAR’s VBS, XP, or HP service. This, of course, means that the ProXRT is a GPS L1/L2 receiver.

I’ll be attending the annual ACSM Conference on Thursday of this week. I’ll keep my eyes open for any other new developments. I’ll probably blog or otherwise comment on the conference somewhere on the GPS World website, as that is becoming our modus operandi when attending conferences. I like that format, and it brings you a bit closer to what’s happening if you are unable to attend the conference yourself.

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