Q. What improvements have been made recently in the signal technology?
A. One of the things that they used to talk about in the early days was how long it would take a high accuracy satellite signal to converge. It used to be that when you turned on a unit, you could expect it to take a half hour to 40 minutes before you could achieve maximum accuracy. That could be a major problem if your signal got blocked, and you had to wait that same amount of time to retrieve the signal again.
We made some modifications, and the latest firmware we are bringing out gets the convergence down to where 10 minutes is a relatively long time. We have discovered, however, that over the last year, this has become less of an issue as users have gained familiarity with these systems and are more comfortable and practiced at handling them. That said, we feel it’s a significant improvement to the system that makes it easier for everyone. GPS manufacturers are still working to implement this change into their products, so while we’ve made it available, it will be a few months or more before the end user experiences the improvements.
Q. What are end users looking for in accuracy?
A. What they are looking for is sufficient accuracy to do planting and strip-till with automatic steering systems. That has been the holy grail for some time, and really when these dual frequency solutions were introduced that was the necessary leap from sub-meter to just a few inches. Now, the accuracy requirements are being fulfilled.
Q. What about repeatability?
A. People talk about repeatability, and with an RTK system properly set up you can achieve it to within an inch. But those people who are receiving a signal 14 miles away from an RTK base station are getting accuracy that is really no better than what we can provide, maybe even less accurate.
With an RTK system properly set up and operating close to the base station, you should be able to come back to within an inch of where you were. Whereas with HP or XP, you can come back the next year and be 3 inches or 4 inches off — but normally, you can see it. In agriculture we don’t operate in a featureless environment — there are guides. I might be off 2 inches, which might not be a big deal anyway because I can adjust to that 2 inches with a nudge, then away I go.
Q. Any changes to the service available?
A. We recently introduced partial-year subscriptions, so if you know you will only be using the signal for part of the year you can order it that way.
Q. Anything new with satellites or satellite coverage?
A. A lot of that is longer term. GLONASS just put up three more satellites that are not operational yet, and they are planning to put up another six in 2008. So looking forward, GLONASS-capable receivers will mean that satellite availability will become less of an issue. Blockage from trees and obstacles will not be as big a problem because you will have additional satellites. We are generating GLONASS corrections and putting them over our satellites, so that is, in one sense, becoming available. It’s there and it’s being used for specialized applications, but the necessary receivers are unlikely to be widely available for agriculture. It will be another year or two down the road before GLONASS-capable ag receivers are common.
Q. Any observations on manufacturers and receiver quality?
A. Each new model that comes out from all the manufacturers has more capabilities — the capacity to track more satellites, lower noise, better accuracy, and more features. I was at a Trimble event recently, and its latest technology is really impressive. But other manufacturers such as Leica and Topcon have terrific new technology, and Hemisphere is just coming out this year with a dual frequency receiver.
Q. Why is dual frequency important?
A. Dual frequency receivers use two of the GPS frequencies, L1 and L2. Up until a few years ago those were exclusively used by surveyors who wanted high accuracy, and because of cost the ag market used only single frequency L1 only. With L1, you really cannot get better than submeter accuracy. People who are serious about automatic steering and planting and strip-till being within an inch or two, need a dual frequency receiver. Dual frequency permits better compensation for atmospheric errors and helps with the complex calculations required for high accuracy (carrier phase) positioning. This is really where the growth is in the market today.