Surveying


Best practices in surveying

Oct 2014 | No Comment
Best practices in surveying are not limited to field procedures and accuracy requirements but must include professionalism and ethics. This paper will look at essential best practice approaches for achieving desired quality surveying products and establishing integrity among peers and clients

Dr Frank Derby

Associate Professor of Surveying, The Pennsylvania State University, USA

Textbooks and scholarly publications describe best practices for using various surveying equipment, capturing and processing field data, and gathering and analyzing evidence. Since there are varieties of surveying activities, ranging from national survey control networks, boundary surveys, construction, hydrographic, topographic, mining, and cadastral, etc., it is fair to say that there are no standardized approaches, which can be classified as “best practices” for practitioners to follow. Evidence and procedures go hand-in-hand with data processing and visualization. For land surveying professionals, the key to producing quality product is to understand the objectives of the client, determining the scope of the project, researching evidence and descriptions, selecting appropriate equipment adopting methods that can produce desired results, based on the required accuracies. In all aspects of the surveying tasks, professionalism, ethics and due diligence are paramount. Professional surveyors should always be aware of their responsibilities to the public and adhere to ethical conduct in the execution of their professional obligations to clients.

Not so long ago, when the essential tool for land surveying was the total station, surveyors accomplished tasks by measuring angles and distances. Coordinates of surveys monuments were tied to coordinated passive control monuments, which had been established at strategic locations in the jurisdiction. The positional accuracies of these passive control networks were classified as first, second and third order accuracies based on angular and linear misclosures of the network. In many jurisdictions, there are state laws, rules and regulations for conducting certain surveying activities such as boundary determination and cadastral surveys. Therefore, in discussing best practices, the focus will be on generic rather than specific tasks. Below are steps that can be taken to accomplish tasks successfully.

Understanding the Purpose and Scope

The first thing for the surveyor is to understand the purpose for which surveying services are being acquired. For large scale survey projects, the requirements from inception to the deliverables will be specified in the Terms of Reference. Therefore, it is the responsibility of the surveyor to understand the requirements and be able to ask questions where necessary. On smaller projects without written Terms of Reference, the best approach is for the surveyor to spend time and confer with the client to discuss the needs of the client in detail so that there are no ambiguities in the expectations. Often times, clients are unable to fully articulate their needs completely. A detailed discussion would clarify the scope of the project, amount of information to be provided, field survey and mapping methodologies, acceptable accuracies and the types of deliverables. An experienced surveyor should be able to ask questions, explain technical issues, discuss options, and to clearly define the services that need to be performed. Based on these discussions, surveyor should be able to define the scope of the project, identify the types of equipment that can get the job done, accuracy requirements, duration of the project, and deliverables.

In determining the scope of the project, it is incumbent upon the surveyor, to record the tasks so that both parties understand, and agree on the types and extents of the service. The identified tasks must be defined in a written agreement, which must include any exceptions by either the client, or the surveyor. To preserve his professional integrity, exceptions which have been recommended by either party, should be included in the written agreement with supporting evidence.

Assessing Capabilities and Resources

Having defined the scope and expectations of the project, professional ethics requires that the surveyor should be able to determine whether he has the knowledge, expertise or personnel to undertake the tasks. It will be unethical for a surveyor with expertise in cadastral surveying to undertake a project to monitor deformations in a dam. Assessment of capabilities should include equipment and other resources that are needed to accomplish the tasks. Assuming that all these requirements are satisfied, the surveyor should then plan the method for successfully accomplishing the tasks. This plan includes selecting the equipment that will produce the required accuracies.

Defining Equipment, Methodology and Accuracies

As technology advances, so does the procedure for conducting surveys and associated accuracy assessment methods. It is important to stress at this point that not all tools are adequate for performing all types of surveys. Best practices include selecting the right equipment for the right project.

In recent times, Global Positioning Systems (GPS) and Global Navigation Satellite Systems (GNSS), Light Detection and Ranging (LiDAR), Unmanned Aerial Vehicles (UAVs) technologies are becoming popular tools on surveying projects. GPS and LiDAR provide three-dimensional coordinates instantly. Therefore, the best practices for using them require an understanding of positional accuracies which are no longer related to measured distances but determined in terms of the reliability (or confidence level) of the data.

With Total Stations, coordinates of positions are determined from measured angles and distances. Most errors occur in the angular and linear measurements. Therefore, accuracies are listed as linear or relative precisions. In the United States for example, the Federal Geodetic Control Committee has defined minimum accuracy standards for terrestrial based control surveys for mapping, land information, property, and engineering in Table 1.

Based on the information from Table 1, if the relative positional error is ±1 cm (2 sigma), the minimum distance between stations in a project will be 1 km.

Field Procedures and Standards

Depending on the type of project and tasks involved, the best practice it to use the most appropriate equipment to get the task completed successfully. It is important for a professional surveyor to know the limitations of the equipment and sources of errors that can affect the desired accuracy. For example, many surveyors are applying GPS/GNSS technologies on projects. In many cases field procedures may be static, fast-static, kinematic, Single-base Real-Time Kinematics (RTK) or Real-Time Network (RTN) GNSS methods. It is important as part of the best practice policy, to understand the suitability of the methodology, with special regard to site conditions, and the possible positional accuracies. Based on the required accuracies, a suitable procedure may be to include post-processing of the data in order to improve the reliability of the results. Generally, the accuracy of RTN surveying depends on many factors including the reference station distances, equipment and its settings, survey procedures, and the survey environment. Accuracy typically is in the range of a few centimeters, and in some cases can exceed, that of traditional RTK surveying.

Boundary Surveys

Projects dealing with property boundary issues involving deed records require special attention. Best practice procedures include deed research to find evidence to the fact that the client actually owns the property, and that there are no restrictions affecting the use of the property in the manner that the client intends to. Such due diligence includes identification of the client’s record boundaries, conflicting record of ownership, actual locations of the boundaries etc. In addition, any exceptions including rights of way, easements, encumbrances, and reversions of any kind which limit the rights of the client. Where necessary, historical information may be used as evidence to support the surveyor’s decisions in the execution if his duties.

Deliverables and Record keeping

The types of deliverable are normally decided prior to commencement of the project. They come in variety of formats. On projects where the surveyors is required to render an opinion, professionalism requires that the surveyor provides the opinion in a written report, graphical representation, electronic files, or in the manner that has been agreed upon. This will avoid misinterpretation and ambiguities. Ethical and professional, the surveyor must render the opinion in a fair and honest manner and within the scope of the written agreement with the client, the scope of his professional knowledge, and supported by facts and evidence which were used to arrive at the opinion. Irrespective of the required format, the deliverable must convey relevant information and organized in a comprehensible manner. Good record keeping is essential. The surveyor’s work is meant to be kept for posterity. Therefore, details of any sketches, field observations, calculations and data capture should be a part of the permanent records of the surveyor. The surveyor must make a habit of keeping copies of field data capture as well as computations and deliverables in the project file. The best practice is to maintain the records in a manner as to support the basis of decisions and determinations that were made regarding the project.

Conclusion

Surveying is a profession of public trust. The educational preparation and experience that combine to make him a professional requires that he operates in a manner that will earn him the public trust that he deserves. In doing so, he has to adopt the most stringent of professionalism. There are no universal rules that define the best practices for land surveying because whereas surveying principles are the same, regulations vary and therefore equipment and methodologies vary in various jurisdictions. Besides, evolving technology is providing opportunities for surveyors to perform the same tasks with different equipment. The best pra ctice is for the surveyor to adopt the methods that will enable him to provide the service effectively within stipulate accuracies by applying professionalism and ethics throughout the process.

References

1. Ghilani, C. D. (2012), Elementary Surveying: An Introduction to Geomatics, Prentice Hall, New York.

2. Ontario Ministry of Transportation, (2013) Guidelines for RT </RTN GNSS Surveying in Canada, Ontario, Canada.

3. New York Society of Lands Surveying, Practice Guidelines., http://www. op.nysed/prof/pels/lsurvguide.htm. Downloaded on September 1, 2014.

4. Federal Geodetic Control Committee, (1989), Geometric and Geodetic Accuracy Standards and Specifications for Using GPS Relative Positioning

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