Essentially, this means that every dual-frequency receiver designed in the 1980s, 1990s, and many in the early 2000s would become virtually obsolete. In the interest of disclosure, that includes my own legacy real-time kinematic (RTK) system.

All current post-processing and RTK algorithms are based on using codeless/semi-codeless techniques of one sort or another. Those of us in the survey/engineering/construction
/deformation monitoring/high-precision GIS industries would be most affected. We are going to get hit in the wallet — hard.

The DoD’s proposal assumes that most organizations will have upgraded their GPS equipment by 2020 and will be using L2C and other modernized signals, so that L1/L2 P(Y) codeless/semi-codeless processing won’t be needed. The DoD states that GPS manufacturers have indicated that the user community needs about 10 years to replace legacy GPS equipment with equipment capable of utilizing modernized GPS signals.This means that any dual-frequency receiver not designed to use L2C could essentially become a paperweight after December 31, 2020. The receiver may still work after that date, but there is no assurance it will continue operating properly. The list of receivers affected is quite long and includes models from all major manufacturers, such as Trimble, Leica, Topcon, Magellan (Ashtech/Thales), and NovAtel among others. One should not assume that all receivers sold today are capable of utilizing L2C. Ask before purchasing.

L1-only receivers such as handheld GPS units, car navigation systems, tracking devices, GPS-enabled mobile phones, L1-only GPS mapping systems, and timing receivers are not affected by this proposal, nor are L1-only RTK receivers. The exception is some newer receivers designed for GIS data collection at the decimeter level. Although not marketed as such, these are dual-frequency and might be affected.

Thousands, perhaps tens of thousands, of reference stations worldwide will need to be replaced. The U.S. Continually Operating Reference Stations (CORS) network alone comprises more than 1,000 receivers. Granted, some are modernized receivers that may only need a minor update, but many others are legacy receivers that will need to be replaced or risk obsolescence. Those 1,000+ CORS receivers service thousands of users monthly. In April 2008 alone, the National Geodetic Survey reported that more than one million FTP requests were made for CORS data.

The DoD says that December 31, 2020, is not a “hard” date. GPS equipment using codeless/semi-codeless techniques may work just fine after that. But the DoD won’t guarantee it will not do something that will impact P(Y) code and subsequently prevent your receiver from performing as you’d expect.

The DoD is developing modernized signals (L2C, L5, L1C) that should be commonplace by 2020. Continued support of semi-codeless would interfere with some new features they want to play with on the military side of GPS. Why support the legacy stuff when the new stuff is better anyway?

Status 2020. Today, GPS users have 31 satellites to work with. As high-precision users, we need every one of those. Just last week, I was stuck in the middle of a field day waiting for a sixth satellite to come into view so I could continue my RTK work.

The DoD’s proposal states that they expect 24 satellites to be broadcasting L2C by 2016 and 24 satellites will be broadcasting L5 by 2018. While the DoD is still only committed to a 24-satellite constellation, they’ve been spoiling us with 30 or more for quite awhile now. It would be hard to go back.

If I’ve done the math right, and the DoD keeps to its current schedule, by 2016 there should be somewhere between 30 and 35 operational satellites. In 2018, there would be somewhere around 37 operational satellites. In sheer numbers, that’s equal to or better than today. That’s not bad; not bad at all.

Triple-frequency receivers (L1, L2, and L5) will be far superior to today’s dual-frequency receivers that utilize codeless/semi-codeless techniques. If you add Galileo on top of that, it’s a no-brainer. I look forward to the day that I’m in the field and have 20 or more GPS/Galileo satellites in view when just last week I was struggling to find six.Lastly, in case you missed it, the DoD stated that if the new satellite schedule were delayed, it would reassess the codeless/semi-codeless sunset date.

All about the $$$. An argument in support of all this states that triple-frequency GPS equipment will be much cheaper at that time. I agree it will be cheaper, but we are still talking about tens of thousands of dollars. The high-precision market is relatively limited in size, is highly technical, and requires complex software, training, and technical support. It’s not like spending $150 at WalMart for a Garmin receiver that you can figure out without reading a manual.

Another argument in support of the DoD’s proposal is that 12 years gives us plenty of time to enjoy a solid return on investment on our current equipment. While I follow that logic, I’ve seen a lot of GPS equipment in the field that is 15 to 20 years old. The stuff just keeps working. I’ve been amazed that my RTK system, based on 12-year-old technology, still cranks up like it did the first time I used it. Maybe it’s more of an emotional feeling than anything else, but as much as I work through the logic, it’s hard to swallow that my $40,000 system has a date with the trash bin.

Codeless/semi-codeless dual-frequency GPS is the core technology for thousands of small- to medium-sized businesses around the world. For those who made that purchase in the last couple of years, the planned obsolescence is not something they want to hear about even if it is 12 years away.

The U.S. Department of Commerce (DoC) has done a quick survey and prediction, to get a rough idea of the dollar values. These figures formed the rationale for a proposed decision to push the discontinue date out to 2020, to give manufacturers and the user base adequate time to re-equip for using L2C and L5. A full-length interview on this topic with a senior DoC analyst appears on page 32 in this issue.

Note that the DoD is seeking comments from everyone around the globe. The potato farmer in Argentina, the land surveyor in Australia, the geodetic surveyor in the United States, and the engineer in Denmark are all encouraged to comment. GPS is a tool that knows no boundaries.

Col. Mark Crews, the U.S. Air Force GPS Chief Engineer, says the GPS Wing is keenly interested in public comment on the proposal. The Air Force estimates there are approximately 250,000 worldwide users of dual-frequency receivers that use P(Y) codeless/semi-codeless.

“We are trying to do everything absolutely the right way in pre-notifying everybody in the world. If anybody has any concerns, please notify us,” said Crews. “We are taking every precaution to transition semi-codeless users to civil coded signals in a stable, measured, and transparent manner by 2020. That’s why we’re taking action now to pre-notify semi-codeless users worldwide and ask for their input by means of the Federal Register’s request for comments.”

Crews further says the Air Force recognizes that dual-frequency GPS receivers “play an extremely positive role in survey, agriculture, and all high-accuracy augmentation systems. We are bending over backwards until we have at least two other civil signals, being L2C and L5, on 24 satellites in time for people to transition.”

The DoC, on behalf of the DoD, is seeking public comments on the codeless/semi-codeless sunset proposal. All comments submitted are a matter of public record and can be viewed by anyone. Time is short, though — the deadline for comments was June 16. As of press time for this issue on June 23, it had already run out.

That concerns me. I think that’s a mistake, not offering enough time. They should allow at least 90 days so the word has a chance to spread.

ERIC GAKSTATTER is GPS World’s contributing editor for Survey and Construction, writing a twice-monthly e-newsletter. He has spent 18 years in the GPS survey/mapping industry as a product manager, GPS user, consultant, and a non-partisan advocate for the GPS user community.