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Home arrow Archives   The American Surveyor     

Product Review: Traverse PC—To Think Like A Surveyor Print E-mail
Written by Tony Cavell, PS, CFedS   
Sunday, 05 April 2015

A 3.707Mb PDF of this article as it appeared in the magazine—complete with images—is available by clicking HERE

Oh, My!
Several months back I had the good fortune to try a new (for me) software package. I am impressed with it and it brought to the fore some history I have been privileged to live through. There has always been a fundamental disconnect between surveyors and practically everyone else. That disconnect stems from the fact that surveyors deal with approximations--measurements--actually, practically, and conceptually. It is an understood phenomenon taught by necessity and proven by experience. Most people live in a world of perceived exactitude; a world of integers, so to speak.

A running joke among professional surveyors is the story of some filing clerk or intern requiring the surveyor to declare which document is correct because two measures are different by an insignificant or minuscule amount. Living in a world of exactitude the clerk knows if they aren't the same, one must be wrong! The proliferation of computers has not improved the situation. In fact, it has expanded the number of "integer people" many fold.

A case in point may be seen in how surveyors' drawings and drawing procedures have changed over time. Once upon a time, the surveyor's notes would be interpreted by following the recitation of experiences along a boundary or traverse. The drawing would be rendered by transferring those notations onto paper in a graphical manner resulting, usually, in a plat. If the intended purpose was a topographic map a favorite tool was the plane table on which the critical observations were recorded to scale and the details filled in later from the contemporaneous notes.

Military surveyors performed topographic surveys, of course. However, they also were called on to determine locations while in the field for ranging and targeting, so in addition to traverses and plane table work, indirect targeting techniques such as resections were regularly employed. The common thread is how the graphical representation resulted almost directly from the measurements.

Surveyors had other tools useful for detecting errors and for calculating areas. Calculating area, particularly for irregularly shaped parcels may be most readily computed by the method of double meridian distances. First the closing error of the figure, or its traverse, is eliminated, or balanced, by rule. Once balanced, the latitudes (northings) and departures (eastings) were used in a straightforward algorithm to arrive at the area. The necessary balancing also served as a rudimentary check for blunders. Other methods for calculating areas were to divide the parcel into triangles and calculate the areas of the several triangles, the sum of which was the total area.

The theory of least squares has been a well-known mathematical application for locating blunders and deriving the most probably correct positions for the angle points of a parcel. Least Squares required far too much computation to be practical until the availability of computers. It was complex and recursive.

The decade of the 1980s saw the proliferation of computer use by surveyors and engineers; both desk-top computers and hand-held programmable calculators. CAD-CAM (computer aided design-computer aided manufacturing) came along about the same time and had hugely significant affect on how surveyors were expected to represent their work. Hand drafted maps and particularly plats while drawn to scale employed useful exaggerations that clarified particular items without overly complicating the overall drawing. CAD was not so forgiving, forcing important items to remain ambiguous (drawn to scale) or complicating the overall drawing with inset bubbles.

The proliferation of CAD was a welcomed and powerful tool for the engineering professions but designing required a different mind-set than that of surveying. Surveyors, especially those working for firms whose raison d'ętre was engineering, were essentially forced to alter their timehonored mind-set to accommodate the requirements of the design environment.

Perhaps the most fundamental changes was that instead of locations being dependent upon distances and angles actually measured, the distances and angles were calculated from the coordinates of the points entered. Of course the points entered were entered as the result of the measurements but the hierarchy of sources was lost and inverted once entered. The second significant change was to change the thought process from one of applying and testing measurements to one of dealing with positions as coordinates.

The 1990s saw the development of geographical information systems (GIS) from the earlier developments of land information systems (LIS) and multi-purpose cadastres. CAD is almost exclusively coordinate based and is attractive because one may by using graphical means marry many layers of maps and database information displaying the results as very persuasive images. One of the several early adverse acceptances of GIS by surveyors was the flexibility of control points, often referred to as "rubber-sheeting." This ability was to stretch or shrink one map so that it overlaid another map or photograph in a desirable way.

There were some attempts to recognize and accommodate the rendition of drawings utilizing the time-honored methods of surveying. Esri created an application that was promising but then dropped it in subsequent editions. CAD software has shell programs intended to use the vocabulary of surveyors but the underlying mind-set is still one of design.

I am a Certified Federal Surveyor (CFedS) and from time to time found need to use the BLM's Geographic Coordinate Data Base (GCDB) and GMM software. The program works but lacks a modern GUI (graphical user interface) and has an interesting set of idiosyncrasies. My attention was drawn to Traverse PC, in part because it could calculate results that were compliant with the GCDB. It also was promoted as accepting input in the same form that surveyors think about it. I received a copy and began working with it.

I found the interfaces and menus pretty straightforward and easy to figure out, even going in cold. With no training, I was able to make my entries and derive the answers I needed. As I progressed to the point of improving the appearance of my output drawings, a quick phone call resolved my curiosity within a few minutes. I learned that the BLM uses Traverse PC for many of their calculations now. Learning that increased my confidence that I had made a wise choice.

I was perhaps most surprised by how strongly the influence of CAD was in my computer habits. I found myself trying to put everything I knew into the system expecting to then sort it out with geometry and within a few tries I figured out the name of the program meant what it says. I needed to simplify my approach because I was trying too hard. What I needed to realize was the program works best when it is approached the way a surveyor approached a job recorded logically much like when using a real paper field book.

Traversing the project boundary is one traverse. Running out a lot is another single traverse. As points are re-occupied they are recalled by simply entering them into the traverse. If the purpose is to check points already run through, a similarly named point is created, e.g., 14 & 14.1 or 234 & 234.1 & 234.2. Rather than using the drawing as the entry point for data, it is the traverse. Getting past that understanding was like taking the blinders off.

Shortly after getting my start with Traverse PC, I was engaged as expert in a couple of court cases that involved properties surveyed by the GLO back in the early 1800s; additionally the sections were of the radiating kind found along rivers in Louisiana. I was able to enter the GLO field notes from the archives to compare how one set of measurements compared to another and to modern surveys. The hardest part was reading from the images of the often torn and faded copies of the original notes. Using the program was a piece-of-cake by comparison. Traverse PC was not the only tool I used but it proved its value to me by the analysis it afforded me that would have been more challenging using other tools.

The ability to think in terms of survey activities, called traverses within the program, one enters measurements or GNSS positions, old control data, sun shots, and more. One or more of the created traverses are enabled to create a drawing. The drawing and/or the traverses have settable properties that dictate how the drawing will look, what bits of data will be annotated and the like. One addition I would like to see for some applications would be a level run input; one in which the azimuth and distance are not recorded or of a useful precision. This can be accomplished now by the user but a straightforward means of entry would be cool and, I bet, a popular use.

The friendly, sometimes jocular, support provided by Traverse PC is just about the most gratifying I've experienced. The FAQs on the website are concise. The phone numbers are provided. The phone gets answered or a call is returned in a timely way. The monthly newsletter announces new features, offers, trends, and tales. Suggestions are welcomed when offered.

My business doesn't involve many boundaries and plats going through my office as in a typical surveyor's office, but if it did, Traverse PC is my tool of choice for entering surveying data. I don't have to eliminate the other software tools but their use can now be what is appropriate for them. Some may be best for downloading GNSS. Others may be best for designing fancy logos or helping the engineers with a roadway or foundation. Yet others may be appropriate for "counting pixels" to determine crop diseases. Thank goodness, Traverse PC is available for use while "thinking like a surveyor."

Tony Cavell is Surveyor/Consultant in Baton Rouge, La. He is a fellow of NSPS and ACSM and vice president the NSPS. He is a past president of the Louisiana Society of Professional Surveyors, and former Associate Director of and current Surveyor/Research Specialist of the LSU Center for Geoinformatics & Louisiana Spatial Reference Center.

A 3.707Mb PDF of this article as it appeared in the magazine—complete with images—is available by clicking HERE

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