December 1, 2008
From the Ground Up
I’ve enjoyed reading Mark Meade’s “From the Ground Up” features in POB for some time and especially appreciated “Elevation for the Nation” (April 2008, August 2008). This initiative is getting a lot of attention lately. However, I find that one critical element is frequently missing from the discussion-the vertical datum.
In the second national LiDAR strategy meeting held [in September at the U.S. Geological Survey offices] in Reston, Va., this question came up, as well. As Mr. Meade stated, there were two days of informative talks. Only toward the end (the QA/QC portion) did the question get raised as to what vertical datum this data would refer to. With GPS in the airplane and purely geometric vectors coming out of LiDAR, the only thing which LiDAR can immediately (and with greatest accuracy) achieve are ellipsoid heights (in the U.S. they would be either NAD 83 or ITRF). However, for flood-plain mapping, orthometric heights are needed. How will “Elevation for the Nation” address this question?
If the plan is to set up GPS base stations over NAVD 88 bench marks (as per “Height Mod-style surveys”), then those who are making such plans should be reminded that most of the data that went into those bench marks is about 30 years old (just like the average data in the NED, as the article points out).
Is the plan to use a hybrid geoid model? While Mr. Meade touched on this topic in his April 2008 article, stating “we have improved geoid models that allow us to determine orthometric heights more accurately than before,” the improved geoid models most people are familiar with are not purely gravimetric geoid models but hybrid geoid models, which are artificial constructs built around gravimetric geoid models and used solely to convert NAD 83 ellipsoid heights into NAVD 88 Helmert orthometric heights with no attempt to fix the known errors in both datums (such as the non-geocentricity of NAD 83, or the decimeters of bias, and meter-wide tilt in NAVD 88 relative to the best gravimetric geoid models).
As such, while a hybrid geoid model can give an accurate NAVD 88 height, it cannot yield an accurate orthometric height since the validity and accuracy of NAVD 88 itself is in question. This is especially critical in the 11 percent of the nation with nearly flat terrain. NAVD 88 heights are not true orthometric heights, and thus LiDAR’s usefulness is hampered without an updated, accurate and monitored vertical datum that is accessed via GNSS technology (specifically, this means a high-accuracy gravimetric geoid model that is monitored through time). This is the crux of a program being initiated by NOAA’s National Geodetic Survey known as GRAV-D (Gravity for the Redefinition of the American Vertical Datum).
Thankfully, a few attendees of the national LiDAR strategy meeting were well aware of GRAV-D, and a very constructive conversation was held in open forum about vertical datums and how best to get good orthometric heights out of LiDAR.
I felt compelled to write and point out this missing detail simply because so much attention is being put on the use of LiDAR for flood-plain mapping but so few people talk about the current inability to get truly accurate orthometric heights out of an effectively ellipsoid-only system. Thank you for your interesting articles and the opportunity to make this important point.
Dru Smith, chief geodesist,
NOAA’s National Geodetic Survey, Maryland
I read a large number of articles about the surveying profession, and most don’t impress me. However, I was very impressed with this article. I think if more surveyors ran their business like a business, we would all benefit. I particularly liked the last paragraph that referenced Washington, Lincoln and Jefferson. At one time, surveyors were the leaders in the community-and the country, for that matter. It appears that attorneys have now taken over that role, but maybe more surveyors should at least strive for that position. If more surveyors were leaders in their business as well as the community, the country as well as the surveying profession would benefit. I look forward to Joe’s next article.
David J. O’Brien Jr., PSM
The Technology Benchmark
I read [Harry O. Ward’s] latest column with great interest. While I wholeheartedly agree that formal education is a must to elevate our status as professionals, I feel Dr. Gibson has denigrated a large group of people who do not and never will seek formal licensure. Technicians are the lifeblood of our business as paralegals are to attorneys and physician’s assistants are to doctors. These are people who will never be doctors, lawyers and professional land surveyors, but without whom the practice of law, medicine and land surveying would grind to a halt.
I find Dr. Gibson’s remarks shortsighted as they are in opposition to the National Society of Professional Surveyors, which is actively expanding a program to create certified survey technicians. What this will do is enhance the knowledge of entry-level surveyors who will then make better decisions on the ground-a necessity as many professional surveyors never see the land their survey depicts. The CST program is not and never will be a path to licensure (it is not intended to be), but it may inspire practitioners to resume formal education. Further, in the state of Florida, there has long been only one university graduating surveyors. Entry requirements and tuition have increased at an alarming rate, while the program has graduated an average of 18 to 19 surveyors over each of the past three years (less in prior years). At the same time, licensed surveyors are dying or retiring at a rate of roughly five or six to every one graduate. This ratio is a prime contributor to the worth of a licensed graduate.
Were UF to graduate as many geomaticians (land surveyors) as all of Florida’s universities do engineering graduates, the value and salary of a new graduate would quickly drop far below that of a new engineering graduate due to the law of supply and demand.
C. Boyd Allen, PLS
The Technology Benchmark
I totally disagree with Dr. Gibson's position. By requiring a four-year university degree, you effectively “lock out” forever many of the older survey technicians with a wealth of experience who, because of financial and/or family situations, can never attend a certified university!
It is true that in our current age of advanced technology, education, as well as a continuing educational requirement, are a must. But it is not where you get it but that you DO get it that counts!
I took my California LSIT exam after gaining 30-plus years of varied, comprehensive experience. All of my formal education was obtained from ACSM and POB seminars, a great amount of home study, and two formal university prep courses. I passed this exam the first time I took it, an almost unbelievable accomplishment.
Need I say more?
Dick Udell, LSIT
The Technology Benchmark
I disagree with statements by Dr. David Gibson, UF Professor. Dr. Gibson states that “apprenticeship programs have been a detriment to the profession.” I believe apprenticeship programs have been the key to the profession for quite some time. However they will disappear because of the technology factor more than any other reason.
[The article notes Gibson’s] view: “These programs have been replacing the college degree, thereby perpetuating the perception that education is not the foundation level basis for surveying. Apprenticeship programs are the continuation of the technician image for the surveying profession.” I am at a loss. What apprenticeship programs have been replacing the college degree?
And the last sentence, I quote again: “Apprenticeship programs are the continuation of the technician image for the surveying profession.” Where is that coming from?
If Dr. Gibson would check the University of Florida program, he would see that no survey boundary law courses are required. UF is actually promoting surveyors as technicians, but just at a higher level. UF has a 120-credit-hour degree program. I note many other B.S. surveying degree programs require much more than the absolute minimum of 120 hours, and they do include boundary law.
I will note that UF requires either an ag/natural resource law (three credits) or business law (four credits) course. I also note that I have six business law credits, three real estate law credits and three boundary law credits, all required at the time by NJIT. I need three more boundary law credits to complete the degree requirements.
Lawrence Paul Lopresti, PE, PLS
David Gibson responds: I welcome your comments because in-depth discussion on this issue is important. When I graduated high school in the 60s, I heard of the field of surveying. I was going to engineering school because of my father's prompting. When applying to university (Penn State and University of Cincinnati), I had to [choose among] electrical, civil, mechanical, etc. I asked someone, “Where do they teach surveying?” The answer came back, “Civil, of course.” I checked that one and now have three degrees in civil engineering. Surveying course work was my first love in undergraduate school.
Only in the ’70s did I find that the “Grinter Report” of 1955 caused a major change in engineering education-away from the lab-based, practical, hands-on subjects of the ’20s and ’30s toward the mathematical and scientific approach (engineering sciences). In 1959, civil engineering (CE) department chairs met at the University of Michigan and voted that civil go along with the other engineering [disciplines] toward the analytic approach. Several topics were “dropped” from emphasis in CE-[including] surveying and construction management. During the ’60s and ’70s (the washout decades), surveying was basically washed out of civil programs. When the last remaining tenured surveying professor retired, they gave the position to structures, hydraulics, etc. Today, there are essentially no tenured surveying professors in CE, and many schools do not even teach a surveying course. The word “surveying” does not appear as content in today’s ASCE’s “Civil Engineering Body of Knowledge for the 21st Century.”
A dual-licensed PE/PLS is a “dying breed” in surveying circles. Perhaps you came into the PLS in the 1980s and ’90s when Pennsylvania stopped automatically granting a PLS to PEs without a surveying exam. The state had to grandfather all existing CEs into a PLS license. As civil dropped surveying, the younger CE grads no longer knew about surveying, no longer cared, and no longer sought dual licensure. Today in Florida, about one out of 400 new CEs may seek dual licensure-they’re the sons and daughters of CEs who had survey experience at the family firm or party chiefs who had survey experience before attending CE school.
As the CE academic influence declined, the apprenticeship system took over. Previously (in the ’50s), apprenticed surveyors were about equally numbered with the CE-graduate dual licensees. That academic input to the surveying profession in the ’50s and ’60s was very important. But the apprentice system basically replaced the former CE college degree practitioners during the ’70s, ’80s and ’90s.
Today, the surveying profession is trying greatly to establish its own educational identity-about half the states have done away with the “experience only” method, many with four-year degree requirements. It’s a slow process, but the profession has made great progress academically. However, the apprenticeship system has “dug in its heels” and won't go away. This feeds the public’s image of the word “surveyor” as a [poorly educated] roadside survey tech. The surveying academic community fights this image daily.
By the way, we at UF cover boundary law very well in two surveying courses: Cadastral Principles, which includes complete coverage of Brown’s book of legal boundary principles, and Surveying and Mapping Practice, which is a comprehensive study of survey situations requiring the application of legal principles.
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