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I recently made a 2,500+ mile road trip to the 12th Annual Surveyors Rendezvous in Council Bluffs, Iowa, and CGSIC/ION in Nashville. Like bookends on a shelf, the trip was a flash back and a flash forward on the story of surveying. Ours is the generation that stands between the bookends–the ones who held a chain in one hand and the first computerized instrument in the other, who continue to witness technology expand at a mind-numbing pace. As always, the Rendezvous was jam-packed with well-organized presentations, fascinating history, engaging side-trips and plenty of good conversation. The extreme hardships our forebears endured as they helped "build" this country have largely been lost to the silence of history; fortunately, the Rendezvous events serve to keep their memories alive.
Milt Denny gave an excellent account of the early GLO surveys. He began with an eloquent reminder of how good we’ve got it today, and the contributions surveyors have made to our country. Few things are built without the involvement of a surveyor. John Thalacker, a well-known Washington surveyor, came to the Rendezvous after visiting the Museum of Surveying in Illinois. He was impressed that in addition to the fine collection of old instruments, the story of surveying is told in a way that makes it easy for non-surveyors to understand its importance. I highly recommend not only visiting the Museum but also supporting it with your contributions. Bart Crattie has written an excellent recap of the Rendezvous which will appear in our next issue.
From Council Bluffs, I drove to Nashville for the 52nd Meeting of the Civil GPS Service Interface Committee (CGSIC) and the Institute of Navigation GNSS conference (ION). CGSIC is a forum in which the military and civilian sides of government meet. This year’s meeting included such topics as Unmanned Aerial Vehicles and intelligent transportation, but to me, the most significant topics revolved around interference and jamming. NGS representatives devoted an entire afternoon to discussing the coming new coordinate systems. Once again the audience was reminded that this is the surveyors’ bailiwick. Passing the expertise off to other professionals would be an opportunity lost.
Javad Ashjaee made a presentation at ION on what his company has done to combat interference. As part of his presentation he introduced J-Shield, which protects all commercial GNSS bands against nearby interferences. Javad also discussed an event that had occurred in Moscow just before ION: something was completely blowing out the GLONASS L2 signal. GNSS receivers sometimes do not work properly and because of built-in "headroom" users are often not even aware that interference is occurring, but Javad’s receivers not only show where the interference is, they provide a way to report it.
I’ve had surveyors tell me they can’t work during certain hours of the day due to "outages," but since there are always other things to do, they just work around them. But here’s an idea: why not find out why they can’t work and report the offender that’s interfering with their GNSS signals? For a long time the U.S. Coast Guard Navigation Center has had an avenue for reporting interference. Once reported, it’s up to the FCC to stop the interference.
The GPS community rose up against LightSquared because the original plan would have squashed GPS signals for existing receivers. But Javad has clearly shown that he can build a filter that will allow his receivers to coexist with LightSquared. The company may no longer make front-page news, but LightSquared has not gone away. In a recent article in Inside GNSS, Editor Glen Gibbons details the current situation regarding LightSquared, and indeed, part of the FCC’s position continues to be that the GPS receivers have been looking outside the assigned frequency bands to gather signals. But as Javad says, interference already exists today that outweighs any effect LightSquared would have had.
Javad suspects that cell companies might be the interference offenders as CDMA cell phones handshake to communicate and pass from one tower to another. Some feel that, particularly in rural areas, to save money the cell companies neglect to install a filter. Unlike Javad’s inexpensive filter, because the cell towers emit signals as high as 1,500 watts, and the GPS receivers are dealing with one or two watts, this makes the cell filters very expensive. Other sources of interference are less identifiable, and in the case of truckers installing jammers on their moving targets to prevent their companies from tracking them, more difficult to catch.
One approach involves identifying sources at toll booths, but both the toll operators and the cell companies have used privacy grounds to delay implementation. In many cases, the offenders are unaware they’re even emitting the interference. In any event, several companies are hard at work devising schemes that will address security problems with receivers. Meanwhile, those of us that use GPS to make money suffer the effects of interference. This plays out by RTK fixes taking 15 seconds instead of three seconds (and who’s not in a hurry when they are standing at the pole?).
I don’t know about you, but I find myself using my iDevices more and more as I untether from my desktop computer. I crave more bandwidth, and am displeased at having to pay $10/Gb for data. Our country needs more bandwidth at less expensive rates. Whether it’s LightSquared or some other provider, the economic benefits are self-evident. What’s not to like about paying as much as two thirds less for mobile bandwidth? Keep in mind that current bandwidth providers have a vested interest in maintaining the status quo.
Marc Cheves is editor of the magazine.
A 1.162Mb PDF of this article as it appeared in the magazine—complete with images—is available by clicking HERE