|RTK vs. RTN|
Real-Time Networks – Laying the Fallacies to Rest
By Jesse Kozlowski, PLS, article from Professional Surveyor Magazine • June 2008
Early implementers of RTN solutions faced considerable opposition for various reasons, including a general lack of understanding of the technology. It took ordinary field surveyors—the best test subjects—to turn negative opinion around. The concept of network-corrected RTK (real-time kinematic) surveying came under fire from the outset. The first academic white papers were met with skepticism, and the developers of early practical implementations and software solutions were criticized by both suspicious late adopters and potential competitors. So, in the late 1990s—the period following initial RTN introduction but before widespread adoption—little authoritative reference material was available to new practitioners, while misinformation abounded. Of the few white papers that were published, and that cited results based on controlled-testing conditions, results seemed too good to be true and/or appeared far out of reach. Sadly, while such published results were oftentimes accurate, it would be several years before RTNs were spread widely enough for independent verification. This combination of lack of information, misinformation, and misunderstanding spawned a number of fallacies about RTNs, fallacies that should be laid to rest once and for all so that they can no longer hamper broader adoption of this valuable new RTK tool.
The Geodetic Premium
There are some who believe RTNs could not be properly implemented unless the user has had formal geodesy training. On the contrary, RTNs are predominantly used in non-geodetic applications. However, RTNs do offer significant potential in this area.The geodetic issue can be addressed from a number of angles. Firstly, users of RTNs are typically more concerned with the inverse between two coordinates, or the angle between three, than the absolute position of a point. Of course, they may wish or need to express results relative to a reference framework, or some published values for control, and so to address these requirements users can apply localization. They can then calibrate or adjust measurements to those values. This method follows much the same principle as closing on known marks for traverses or level runs. So, an RTN is more than sufficient for typical applications.Secondly, unlike users, who, as stated, may often not be concerned with absolute values, RTN operators must be very cognizant of the underlying geodesy, especially in areas of tectonic movement, and must constantly monitor the relative positional integrity of the reference stations.Finally, the U.S. National Geodetic Survey (NGS) organization, acknowledging the strength and potential of RTNs, currently has a task group working on guidelines for proper implementation and use in geodesy. This NGS involvement has done much to diffuse the controversy over geodesy and RTN. Similar activities have been taking place around the world for some time, typically wherever RTNs are already fully implemented.
White Papers - Publishing Real Research
White papers are usually published by academia or the scientific community
to communicate the results of closely controlled tests or other research. But in the 1990s, before third parties really began to take notice of RTNs, many white papers and reference materials were generated by organizations with their own agendas or a financial stake in the subject. Resembling brochures more than they did white papers, these publications offered no practical assistance to potential or existing users and operators. Now that the scientific community is taking RTNs seriously, the quality and integrity of these white paper materials have improved greatly by providing detailed, accurate information that can be relied on.Is an RTN Solution the Only Tool You Need?
The short answer is, no. RTNs are an excellent tool, saving an enormous amount of time, and, of course, cost. However, other tools in the surveyor's kit may occasionally be more appropriate in a given job. For example, RTNs will not replace total stations and will not make monuments obsolete. Additionally, they will not relieve surveyors of the responsibility of following solid surveying practices and independently verifying evidence.Some users have de-scribed RTNs as "magic tape," enabling them to relate two or more positions with great speed, repeatability, and precision, but only if proper procedures are used to "close" on those sets of observations to verify the measurement. However, even with this additional step, RTNs save more than sufficient time to offset the cost of additional gear and independent verification.
Brand loyalty is not necessarily a bad thing. It is inevitable, and fostering loyalty is a good business practice for manufacturers. But, in the case of RTN, such loyalties were sometimes exploited in ways that did great disservice to the subject. Customers who have good success with their gear will very likely choose the same brand in the future. However, RTN is more of a solution than a traditional piece of hardware and software. Forward-thinking manufacturers are moving into more holistic approaches to work processes.The dialogue sometimes became a little too "noisy" and we have just examined several examples of this. Posturing over perceived advantages or disadvantages in particular solutions sounded more like comparisons of hardware features, not as whole solutions. Claims and counterclaims were usually not backed up by any empirical data; head-to-head tests have been few, with fewer still meeting any criteria that would be considered truly controlled conditions. Promoters of particular solutions sometimes spent far more time denigrating a competitor's solution than clearly demonstrating the value of their own. Ironically, most networks provide multiple solutions, including those that may have previously been considered competing solutions.Why have some solutions become more widespread than others? The answer is in proven track records, excellent support, and wide communities of supportive peer networks, i.e., the quality of the whole solution rather than individual features.One operator of a successful RTN in its sixth year of operations put it like this: "At times it seemed like the old Beta-VHS war," alluding to the VCR-tape format battle of the 1980s. "Did it really matter if it was Beta or VHS, or was what really mattered the quality of the movie you watched on it?" What really mattered was the quality of the movie—and where you could get the movie. So too with RTN.
Tried and Tested
Over the last decade, despite many hindrances, RTN technology has proven its worth, and today hundreds of successful networks are installed around the world. Slowly but surely, the noise of doubt and debate is dying down, enabling users to determine, with greater clarity, what employing or operating an RTN has the potential to offer them, and their business.
JESSE KOZLOWSKI, PLS, is director of surveying technology at Taylor Wiseman & Taylor in Mount Laurel, NJ. With offices throughout NJ, PA, MD, and NC, Taylor Wiseman & Taylor operates in all surrounding areas.