Surveying and Land Information Science

Vol. 63, No. 3 (2003)

 

Statistics and Adjustments Explained

Part 2: Sample Sets and Reliability

Charles D. Ghilani

 

The normal distribution is based on a population of observations. Surveyors only collect a small sample of observations from the population. The size of this sample can vary from several observations to one observation. As can be expected, reducing the number of observations will affect the reliability of the sample. This paper looks at statistical testing of samples and their relationship to least squares adjustments. In particular, the paper explores the t, 2, and F distributions and their uses in least squares adjustments.

 

 

Forest Cover Change Assessment for North Central Florida Using Landsat Thematic Mapper Data

Levent Genc and Scot Smith

 

Land cover change and its temporal trends were assessed between 1985 and 2000 in an area in northeastern Florida primarily covered by pine plantations. Landsat imagery was the principle sensor employed and the image processing techniques included the normalized difference vegetation index and a combination of supervised and unsupervised classification techniques. Results showed that during the 15-year period, mature pine plantation cover and young pine plantation cover declined by 9 percent and 2 percent, respectively, while open field increased by 10 percent. It was also determined that wetland forests declined by 5 percent. Because trees serve as highly efficient carbon storage devices, the decline in forest cover (pine plantation and wetland trees) leads to increased pollution of the atmosphere with carbon dioxide.  

KEYWORDS: Image classification, forest, remote sensing, deforestation.

 

 

Software for the User Interface of Coordinate Rubbersheeting in Vector-based Geographic Information Systems

Arthur J. Lembo, Jr. and Thomas D. O’Rourke

 

Rubbersheeting solutions for improving the positional accuracy of map products have been in use for over 20 years.  Early attempts to utilize rubbersheeting methods were infrequent, as most software was developed within an organization and required skilled programmers and other collaborators with backgrounds in computational geometry, surveying and engineering, and mathematics. Additionally, the software used to perform rubbersheeting often relied on separate programs written in Fortran or “C” and was run separately from the geographic information system used to digitize the data. Innovations in the use of graphical user interfaces with geographic information systems have made rubbersheeting algorithms easier to apply in commercial software systems.  While the ease of use has made these powerful techniques more available to the practitioner, much of the theoretical concepts behind their use are hidden, which may lead to inappropriate applications of the techniques. This paper presents a brief history of the development of rubbersheeting solutions for geographical information systems, illustrating the evolution of software interfaces and the need for increased literacy in the use of the technology.

 

 

New Approach in Using eRTK-GPS for Direct Georeferencing of Aerial Images in a GIS Application

Stacey D. Lyle, RPLS

 

The purpose of this paper is to describe the research conducted in the development and preliminary testing of a real-time georeferencing method for a small-format digital aerial camera system using new methodologies in extended Real-Time Kinematic Global Positioning System (eRTK-GPS) solutions. This system is being developed to supply the U.S. Department of Agriculture Farm Service Agency (USDA FSA) with aerial digital images that would replace the current 35 mm slide film method and facilitate the development of a geographic information system (GIS) for crop compliance support. The direct georeferencing method was developed by the University of Georgia and Texas A&M University-Corpus Christi in fulfillment of the National Aeronautical Space Agency’s (NASA) contract for developing new technologies and methodologies in remote sensing. The research included development of eRTK-GPS in an aerial platform where differential solutions 35 kilometers from the base-station generate two-centimeter and five-centimeter accuracy horizontally and vertically from the digital camera exposure station’s location. A real-time georeferencing system results in a world file with affine transformation parameters without the need for post-processing GPS or ground control points. Flight tests were conducted in Georgia and Texas with different wireless communication systems to assess the robustness of the solutions on an aerial platform.

 

 

U.S. and Pennsylvania Law of Monuments as Evidence

Preston Hartzell and Wesley Parks

 

National and Pennsylvania law of monuments as evidence is examined. General considerations are developed from standard land surveying and legal sources. Federal statutes on monuments as evidence and a representative case are reviewed. Pennsylvania statutes and a representative case are reviewed. A hypothetical land surveying situation involving monuments as evidence of boundary location is presented. Principles developed from the review of law are applied to resolve the situation.

 

 

A Student Recruitment Program for Geomatics

James A. Elithorp Jr., Ph.D., P.L.S.

 

The typical geomatics program is an expensive investment in faculty, equipment, and computer hardware/software. Most geomatics programs operate at a reduced level due to the lack of qualified students. Active recruiting programs to increase the student population are expensive in time and funding. Limited educational budgets for recruiting require that such efforts be maximized for impact. This paper examines why students choose geomatics as a career field and seeks to identify the important elements of a successful active recruiting program. Surveys were conducted with working professionals in Alabama and geomatics students attending the Troy State University Geomatics Program. Three important factors were identified as primary influences on the decision to study geomatics: the family; working for a surveying and mapping firm; and attendance at Troy State University. The working professionals identified ten major student recruitment selling points: 1. Working outdoors; 2. Potential for business ownership; 3. Society needs geomatics professionals; 4. Work in one’s hometown after graduation; 5. Enjoyment of the profession; 6. Challenging and interesting work; 7. Satisfying nature of boundary retracement; 8. Use of high technology; 9. Mathematical challenge of the work; and 10. High demand for graduates.

 

Letters to the Editor

 

Dear Mr. Hixson,

I read with pleasure your paper in the current SALIS journal, “Creating a National Standard of Survey.”  I, too, have been delivering seminars and workshops on the ALTA/ACSM standards since about 1992, having worked with Mary Feindt on their revisions. I offer a few comments and observations:

 

In your proposed “Boundary Resolution” section you make reference (under Parcel Matrix) to the client wondering as to whether all boundary lines need to be surveyed. It has been my observation that such language always acts as a loophole through which the more rigorous requirements will disappear as clients seek to reduce the fee.

Under “Analysis and Resolution” you make reference to surveyors determining legal principles and reconciling discrepancies by “whatever means are legally available to the surveyor.” I agree that this is, or should be, within the scope of the surveyor’s responsibility but have doubts as to the average surveyor’s knowledge of the law—and self confidence in the role—to actually carry it off!

 

Your reference to the possible need for ACSM (now probably NSPS) to champion this cause on its own is well taken. My experience with the ALTA people suggests they are loath to do anything that might make the surveyor’s role more expensive by requiring this Record of Survey.

I am in favor of a national standard to “spell out the principles behind a quality boundary resolution” and agree that ACSM (NSPS) is the institution to introduce the concept. I doubt, however, that state boards of surveyor licensure and registration will adopt it as a rule, at least in the near term. The more likely course will be for the national association to set the standard then let the courts recognize it as a national standard ruling over local practice. This happened in the Bell v. Jones case some years ago when the local court recognized the ALTA/ACSM standard as a national standard even though the case at bar was not a land title insurance matter.

 

I hope that the professional practice committee of NSPS takes your article very seriously. We do need to elevate the standards of practice, much as the ALTA/ACSM document has done, and if our national association is to prove its viability this is the sort of a project it should undertake. My only reservation is concerning the current professionalism and educational advancement of surveyors across the country. My article in the August POB Magazine highlights the case of surveyors in one state not being able to agree on even such basic definitions as positional error.

Once again, I support your proposal and I applaud your article as a practical essay on a subject of vital importance to the profession. It should be of interest to every practicing professional surveyor and, perhaps even more so, to the next generation of surveyors now in their educational and training years. In fact it is the generation of younger surveyors who are or have already been through university degree programs in this country who will be able to enact and work with the process you propose.  For those of my generation it will be a harder sell.

[Robert W. Foster, PE, PLS]

 

 

Dear Editor: Re: R. E: Lee Hixson: “Creating a National Standard Record of Survey,” SaLIS, vol. 63, no. 2, June 2003

 

I was inspired by Bob Foster’s response to Hixson’s recommendation to make property boundary surveys “explicit” rather than “implicit,” as we do now. As another surveyor once wrote, “In the long run, men hit only what they aim at. Therefore, though they should fail immediately, they had better aim at something high” (Henry David Thoreau, Walden, 1854).

 

Hixson has indeed aimed high. I would agree with Bob that for many surveyors of the past as well as the present, it will be difficult to convert to higher standards. As far as future surveyors are concerned, it remains to be seen. Much will depend on their mentors and teachers. Whether and how they instill conscientious professionalism in young minds and set an example will determine the future practice and habits of those minds. Do as I say and do as I do should be synonymous.

Hixson’s concern, based on years of experience with less than adequate boundary surveys by others, and his idea to make a change for the better, are well taken. His outlines of the ALTA/ACSM Record of Survey and Boundary Resolution Statement describe how our less than well organized cadastral system—if one can call it a system—can and should be improved. Back in 1980, the National Academy of Science published a report entitled Need for a Multipurpose Cadastre. The panel recognized our dilemma of floating parcel boundaries—I call it “the floating island disease”—and made recommendations similar to Hixson’s suggestions.

 

I, too, would not want to let a client decide which boundary lines he or she wishes to have surveyed. Even if only one line needs to be staked out in the field, only the expert—the surveyor—can decide which lines need to be surveyed in order to arrive at the correct solution for the location of that line desired by the client. I do see, however, Hixson’s optimistic faith in his peers as a serious obstacle. To get the process moving, he recommends that surveyors could “voluntarily choose to comply.” Human nature being what it is, and title insurers and their attorneys aiming to minimize costs to their clients, voluntary compliance may be more difficult to achieve than Hixson’s expects. Title insurers must be convinced that improved surveying standards will ultimately reduce their liability and potential losses.

 

Needless to say, I wholeheartedly support the idea of an improved Record of Survey Standards and Boundary Resolution Statement. It should be a challenge for the ACSM/NSPS leadership, and adherence to them must become more than voluntary in order to be effective. If the proposed standard is to have any impact and a chance of survival, it is mandatory that ALTA be involved in its improvement together with ACSM.

Gunther Greulich, PLS, PE, Fellow and Life Member, Former president, ACSM

 

Hixson to Greulich

 

Dear Mr. Greulich, Thank you so much for your recent letter. Your comments were insightful and appreciated.

 

And yes, I have this bad habit of “aiming high.” But I cannot help it …especially after running across all the inadequate maps that I have, over the past years. It pains me to see so many surveyors doing such poor work.

But what surprises me the most is that our state laws do not spell out what is required of surveyors when doing a boundary survey! It’s as if we simply assume they will follow good practice, and trust them to do so.

 

As for my decision to suggest a voluntary approach to new standards, this was a direct result of my article last year in Professional Surveyor (where I made many of the same points). I was chastised by surveyors from all around the country for attempting to “micro-manage” them...and criticized for wanting yet another layer in an over- regulated country.

 

Personally, I think that state law should require the ingredients of a proper boundary survey. But in addition, our codes of ethics should contain the same principles. We should also push the concepts in continuing education, and in the ALTA Standards. We should leave no loopholes for the lazy to take refuge

 

I am sincerely disappointed in my profession in this regard. But thank you your support, and I only hope that there will be a ground swell of additional support, leading to real change at the highest levels.

 

Thank you again for taking the time to write me. Do what you can to spread the idea in your state, and maybe we will live long enough to see some progress. I would really like to be able to put a Boundary Statement on my maps some day.

R. Lee Hixson, PLS, Hixson Surveying, 1497 Gray Avenue, Yuba City, CA  95991