The GPS Observer
It's a rare occasion when I write about something other than GPS, but not long ago I was reminded that surveyors should not pay so much attention to technology that they forget the basic principles of surveying, and I wanted to share this important reminder with POB's readers. In late 2005 I attended an all-day seminar presented by Walt Robillard, PLS, Esq., on technology in boundary location. Robillard, along with Don Wilson, LLS, PLS, RPF, introduced the fifth edition of Evidence and Procedures for Boundary Location this year
(March 2006, ISBN: 0-471-6944-7, www.wiley.com). Robillard's handout for his seminar was a document containing a one- or two-page summary of each of the 19 chapters in the book. In each of these summaries, he gave the scope and a list of principles covered in that particular chapter. For this article
I will reference only two chapters: "Chapter 4: Technology as Evidence" and "Chapter 6: Measurements as Evidence." As one of
the attendees at Robillard's seminar, I came away with a renewed sense of how technology can aid us in upholding the underlying principles of boundary surveying.
Technology as EvidenceChapter 4 is completely new to the fifth edition of the Robillard-Wilson book, and the authors state that it was "precipitated as a result of numerous surveyors, who are inexperienced with understanding evidence, placing their full reliance on modern technology." Principle 1 of this chapter states:
All original corner locations or positions are a product of two measurements:
(a) angle (course) and
Not many surveyors, other than those employed by the U.S. Bureau of Land Management (BLM) and other government agencies, establish original corners. But this is a good point to begin our review; as we continue we see how carefully technology must be used in relation to basic principles of boundary surveying, such as that stated in Principle 3:
All corners and lines created by the original surveys should be equated in relationship to the standards of precision that were in effect at the time the lines and corners were created.
For example, the introduction of electronic distance measurement instruments (EDMs) in the latter part of the last century was an advancement in technology that has been accepted as a replacement for the Gunter chain and steel tape for measuring distances.
Three more of Robillard's principles (4, 6 and 7) must unquestionably be followed by the boundary surveyor.
Principle 4: Any error present in the original surveys will be in either direction (bearing) or distances, and these two error possibilities should not be considered to be in a direct relationship to each other.
Principle 6: The positive position of the original corner locations (positions) must be predicated on the recovery, identifications, and interpretation of original evidence and not on applying modern measurements by the retracing surveyor.
Principle 7: A surveyor cannot use more modern precise measurements of course (angle) and distance to set a lost corner but only as supportive or combative evidence in support of lesser evidence.
However, the eighth principle of this chapter can create heated discussion among surveyors.
Principle 8: An original corner, once created, cannot be replaced or redefined by coordinates created by modern survey measurements using more precise modern methods.
In my home state of New Mexico, a PLSS state, surveyors are occupying many original corners with GPS receivers and giving each a NAD 83 position. What Robillard means in this eighth principle is that even if you have an accurate geodetic position for a corner, that position cannot be used to define the corner.
In his seminar, Robillard said, "Technology is not evidence, but evidence depends on technology in its creation and future retracement."
Measurements as EvidenceChapter 6 of Robillard's book continues with the theme of technology but relates it to legal aspects of surveying. As an attorney at law, much of Robillard's experience is in the courtroom defending a survey. He reminded his seminar attendees that "technology cannot be a substitute for legal principles or law." This statement applies directly to:
Principle 2: When modern measurements are related to original measurements, the analysis must be in terms of the original creating units of measurement and not in terms of the more modern units of measurement.
For example, when surveying Spanish land grants, surveyors must be aware that the original unit of measure was the vara. In the reference book Definitions of Surveying and Associated Terms published by the American Congress on Surveying and Mapping (2005), there are approximately 1 1â2 pages listing different definitions of the vara. A vara in Arizona and New Mexico is 33.00 inches; in Texas, 33.40 inches. In California, the length varies from 32.953 inches to 33.372 inches in various records and reports. Modern surveyors must take these various definitions into account when performing boundary surveys on these lands.
Surveyors must also conform to Robillard's third principle:
Principle 3: It is the responsibility of each surveyor to verify the length of the tape or calibrate the distance-measuring device under specified field conditions to a known standard. This includes maintaining the necessary records to show compliance.
Today GPS is the major instrumentation used in surveying. In my opinion, it is ideal instrumentation for breaking down a section of land in public land states. Real-time kinematics (RTK) instrumentation is a GPS total station used extensively in all types of surveying and mapping. Robillard said, "Courts love GPS because courts love numbers." But he also said, "Courts look to measurements as the last resort to evidence." His sixth principle states:
Measurements may be used to prove the validity of corners and monuments. Such monuments, to be acceptable, should be within reasonable proximity of the record measurements.
There is nothing more frustrating to a knowledgeable boundary surveyor than when he or she locates a corner only to find upward of 10 different rebars at the location. All of those rebars were positioned by surveyors using modern instruments and not willing to accept another rebar a few tenths of a foot away. These are often referred to as "pincushion corners."
What Lies AheadWith the continuing implementation of technology, it will be interesting to see what happens in the future. As time goes on, we may be a nation where every survey is like that in parts of Europe today where every property corner has a coordinate.
Many years ago, while working for Wild Heerbrugg, I went to Switzerland to attend a training session on the company's new computer/software system. To gather data for this training, we went as a group to a small neighborhood near the factory to survey the boundary of two adjacent houses. Each property corner was prominently marked with a brass plug embedded in a concrete post, located at ground level.
Because I was from the States, I took one of the total stations (called Tacheomats in those days) and started by positioning the instrument over one of the property corners. After I had the instrument level, one of the group members from Norway asked what I was doing.
He told me that they don't survey property that way in Europe. He walked onto the street in front of the next property to the east and showed me a brass box, embedded in the blacktop at the street centerline. He reached down and unscrewed the top of the box to expose a surveying control point, approximately 6 inches below road surface. "This is the control point," he said. He walked along the street to the west and found another brass box about 100 meters away containing another control point. The accepted procedure was to occupy the first control point with the total station, backsight to the second control point, and then measure angles and distances to each visible property corner. After this, the total station was moved to the backsight point, oriented to the first control point, and angles and distances were measured to the same visible property corner. For the non-visible property corners on the back of the two properties, we had to go to the street behind the house and repeat the procedure. All property corner coordinates were computed; none were occupied. The control points in the middle of the street had plane coordinates assigned to them, similar to our state plane coordinate system in the United States.
Wisconsin is one state that has established a system similar to the one used in Switzerland. Technology has certainly come to the world of boundary surveying, and will continue to influence the future of this work. However, we must not forget the basic principles of surveying as equipment and processes advance. Listening to Walt Robillard was an interesting experience; I, for one, am going to buy the new edition of his book.